DAVIS-BOURNONVILILE 
OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



LECTURES 



DAYIS-BOURNOS^VILLE WELDIN© HfSTITOTE 




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DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDIING and CUTTING 

COURSE OF INSTRUCTION 



Lectures 



WELDING AND CUTTING 

WITH THE 

OXY-ACETYLENE TORCH 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Form 399 



<s^ 






A 



Copyright 1919 by the 
Davis-Bournonville Company 



^ 



©CM530631 



LECTURES 



Combustion. 

Flame and Its Structure. 

Regulating the Gas Supply. 

The Oxy-Acetylene Torch. 

Explosive Gas Mixture — Flashbacks and' Backfires. 

Heat and Temperature. 

Oxygen and Its Manufacture. 

Acetylene and Acetylene Cylinders. 

Acetylene Generators. 

Oxy-Acetylene Welding. 

Expansion and Contraction — Preheating. 

Preparing the Joint for Welding. 

Welding Rods and Fluxes. 

Shape or Mold Welding. 

Welding Dissimilar Metals. 

Gas Welding Machines. 

Testing Welded Joints. 

Brazing. 

Gas, Electric and Thermit Welding. 

Gas Pipes and Manifolds. 

The Cutting Torch and Its Use. 

Gas Cutting Machines. 

Care of the Eyes — Safety Considerations. 

Glossary. 



FACULTY 

Stuart Plumley, Director. 

G. E. Harcke, Chief Instructor. 

F. J. Napolitan, Instructor and Research Chemist. 

Fred E. Rogers, Author of Lectures and Workroom Exercises. 

H. L. Rogers, Chemical and Research Engineer. 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

COMBUSTION 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J, 



Form 375 



Copyright 1919 by the 
DAVIS-B0URNONVILI.E Company 



] 18 1919 



COMBUSTION 

The Blacksmith's Forge — The Ait Blast — Why the Blast Makes the Fire Burn 
Hotter — Welding — Fuels or Combustibles — Heat and Temperature — Oxygen, the 
Supporter of Combustion — Conditions Required for Perfect Combustion — The Oxy- 
Acetylene Torch. 

You are to learn how to make welds with the oxy-acetylene 
torch and to study the construction and principles of the apparatus. 
These are simple but like many other simple matters they require 
clear understanding. Before taking up torch welding in detail, 
we will give a little study to the blacksmith's forge, and forge 
welding. If you first clearly comprehend the principles of the 
forge fire you can more easily comprehend the oxy-acetylene 
torch and its operation. You will see more clearly why it is such 
an efficient welding tool when handled by a skilled workman, 
and will be more likely to avoid making those mistakes that result 
in poor welds and waste. 

The blacksmith welds two irons together by heating them in 
his forge until the ends are white hot and dripping, and then he 
beats them together on the anvil with rapid blows of his hammer. 
The blacksmith can make welds because his forge fire raises the 
iron to such a high temperature that it is melted on the surface 
and is soft like putty throughout. When he lays the two hot ends 
together they stick, and the hammer blows force the soft semi- 
liquid parts intimately together. The blacksmith depends first on 
getting the correct welding heat, and then on skillful hammering 
to make a sound weld. Hammering is necessary to make a good 
scarf weld when heated in the open forge, but other methods 
may be used to make a sound weld when the metal is at the fused 
or welding heat. Good butt welds may be made by simply forcing 
the ends together by pressure when at the proper welding tem- 
perature. Welding may be done in a furnace with no hammering 
or pressure at all except the weight of the metal itself. It is 
merely a matter of getting the metal hot enough, and keeping 



the scale and foreign matter out of the weld. The semi-liquid 
metal will run together and be solidly united when cold. 

Let us examine a blacksmith's forge and see what it consists 
of. The ordinary forge has a plate or table for a fuel bed. In 
the center of the table is an opening through which air is admitted 
from beneath. This part is called the tuyere. Connected with the 
tuyere by a pipe is a fan (or bellows) for forcing air through 
the tuyere to the fuel bed above. The fire is supplied with air from 
beneath; it burns fiercely if the air is forced through it rapidly. 

A much hotter fire is obtained in a blacksmith's forge than is 
possible in a fire built on the ground. The blacksmith can melt 
cast iron and burn steel. It is quite impossible to melt cast iron 
in an ordinary open fire. "Why is it possible to get so much 
greater heat in the blacksmith's forge?" The answer is — "Because 
the fire is fanned by the blast." "But why does fanning the blast 
make it burn hotter?" "Because it gets more air." But this does 
not really tell why. In order to explain the action clearly we 
must first give a little study to what fire is. 

Combustibles or Fuels 

We say fire burns. But what is it that burns or consumes? 
It is fuel in some form or other, such as wood, charcoal, hard 
coal (anthracite), soft coal (bituminous), coke, tar, petroleum, 
fuel oil, kerosene, gasoline, hydrogen, illuminating gas, acetylene, 
and in fact, anything combustible. All fuels are combustibles, 
which means that they are materials that burn in the atmosphere 
when raised to a sufficiently hig'h temperature. Fire then is com- 
bustion. The temperature at which combustion begins, is called 
"the point of ignition." The ignition point varies with different 
materials. The ignition point of soft pine is comparatively low. 
Advantage is taken of this fact in making matches. A match is 
tipped with a point containing sulphur or some other chemical of 
comparatively low igniting point which burns freely. "Over the 
end of the sulphur tip is a thin coating of phosphorus. Now 
phosphorus has a very low igniting point, and sufficient heat can 
be produced by drawing the match head over any rough surface 
to set it on fire. The phosphorus ignites, and in burning it pro- 
duces a sufficiently high temperature to ignite the sulphur. That 



in turn burns hot enough to ignite the soft pine stick, and there 
you have progressive action when you strike a match — a series 
of combustions, starting with the phosphorus and ending with the 
soft pine. 

Anthracite, or hard coal, is difficult to ignite. It was, several 
years after anthracite was discovered' in Pennsylvania before it 
was used as fuel at all. Nobody was able to burn it because no 










Fig. 1 



f^ 






Fig. 3 
Davis Bournonville Institute 



THE BLACKSMITH S FORGE AND THE OPEN FIRE COMPARED 



one knew just how to set a mass of it afire or what were the con- 
ditions necessary for its continuous combustion. The claim is 
made that the conditions required were discovered by accident. 

An open fire built on the ground, even if supplied with the 
most easily burned materials, soon reaches its ma.ximum tem- 
perature, and no amount of new fuel supplied will preceptibly 
raise the temperature. You will get a much larger fire but not a 
hotter fire. Here is a very important point which should be clearly 



understood. A large fire does not necessarily mean a very hot fire. 
The fuel bed or flames of a large fire may never rise much above a 
temperature of 2000 degrees Fahrenheit. 

Heat and Temperature 

We said that a large fire does not mean necessarily a very 
hot fire. There will be much heat given' off but the temperature 
will not rise above a certain point. It is somewhat the same as a 
glass of ice water and a barrel of ice water. The glass of ice 
water is just as cold as the water in the barrel. If we had forty 
barrels of ice water they would be no colder than the glass full. 
So it is with a large and a small fire. The temperature of the 
small fire may be as high as the temperature of the large fire. The 
amount of heat given out by the large fire, however, will be more 
of course than given off by the small fire. The larger the fire the 
greater the amount of heat. But the temperature does not neces- 
sarily increase with the size of the fire. This is important to 
remember. 

In the blacksmith's forge we have a comparatively small fire 
consuming the fuel built up over the tuyere. The blast from the 
bellows or fan causes the fire to burn very brightly and fiercely. 
It burns so fiercely in fact that the blacksmith must be careful 
to build his fire so that he does not burn the metal that he is 
trying to heat to a welding temperature. The fire continues to 
burn if we turn a pail over it, but if we put a pail over an open 
fire it quickly goes out. The reason why the forge fire continues 
to burn when covered with a pail and why it burns so much hotter 
than the open fire on the ground, is that the air is forced through 
it from beneath by the bellows or fan. The open fire is supported 
only by the air around it. The blast fans the fire and blows air 
all through it. It is evident that the air supplies some element 
necessary for combustion. What is this element? It is the part 
called oxygen. 

Oxygen the Supporter of Combustion 

The atmosphere or air around us, is composed of about one- 
fifth oxygen and four-fifths nitrogen. Nitrogen is an inert gas 



that does not support fire but hinders it. The oxygen in the air 
is the supporter of all combustion. It is the so-called life-giving 
element in the atmosphere that we breathe into our lungs. The 
oxygen enters the lungs and purifies the blood coming in from the 
veins, changing it from a dark, almost black, to bright red. This 
action is a kind of combustion in which the impurities or carbon 
in the blood, are burned out. The temperature of this combustion, 
of course, is very low, being 98.6 degrees F. in health. Rusting 
of iron is a slow combustion of the iron due to oxygen in the 
air, and moisture. 

There is a limit to the temperature that can be produced in 
the forge. While the blacksmith is able to melt cast iron and 
burn steel, he cannot do much more economically. It was dis- 
covered years ago that if the air supplied to the blast is first heated, 
a much higher temperature can be produced. It doubtless has oc- 
curred to you that is contradictory that a blast of air makes a 
fire burn hotter. You know that in summer when very warm you 
take advantage of the blast produced by a fan to cool you off. 
Now as a matter of fact the blast in the blacksmith's forge which 
makes the fire burn hotter, also tends to make 'it burn cooler. 
How is this explained? The blast makes the fire hotter because 
it supplies a greater amount of oxygen, but at the same time it 
tends to cool the fire because a large volume of comparatively 
cold nitrogen is forced through the fire. Now if this nitrogen is 
heated to a comparatively high temperature it will not have so 
great a cooling effect as when introduced cold. This is taken 
advantage of in the open-hearth steel furnace. The open-hearth 
furnace is so constructed that fire-brick checker work is heated 
to a high temperature by the waste hot gases, and then by turn- 
ing a valve or damper the cold air blast is forced through this 
checker work and is thereby heated to a high temperature before 
reaching the fire. The result is that a temperature of over 3000° 
F. is produced, ample for melting steel. 

Conditions Required for Perfect Combustion 

When coal is consumed the combustion produces invisible 
gases, smoke and ashes. The ashes are the mineral content of the 
coal that is incombustible. The smoke is unconsumed carbon 



while the gases are the product of combustion and consist chiefly 
of carbon dioxide and water vapor, or steam. Incomplete com- 
bustion and impurities in the fuel limit the temperature that can 
be produced. Perfect combustion can be secured only with pure 
fuels and sufficient oxygen supply. In short, ideal combustion 
can be produced only when the fuels consists only of the neces- 
sary combustibles and oxygen, and when they are supplied in 
exactly the right proportions. 

Hence, if we are to get perfect combustion and high tem- 
perature we must reject all solid waste matter like ashes and also 
all waste gases which dilute the fuel or oxygen supply, hinder com- 
bustion and carry off heat without doing good. The most effi- 
cient combustible gas we can use is acetylene. This gas is simply 
produced by slaking calcium carbide in water, and is carbon 
and hydrogen chemically combined. Both carbon and hydrogen 
are good fuels but when combined they make a much better fuel — 
one that produces an intensely white flame when burned with 
proper air supply, and if burned with pure oxygen the temperature 
produced is amazingly high, being about 6300 degrees F., or higher 
than any other flame known except the electric arc. 

The Oxy- Acetylene Torch 

We have here the oxy-acetylene torch which — as the name 
indicates — uses oxygen and acetylene gases. 

How is it possible to produce so high a temperature in so 
so small a fire as the torch flame ? The answer is "By getting rid 
of everything but that required for perfect combustion." If we 
could get rid of the excess nitrogen in the atmosphere, when blow- 
ing a forge fire, it is evident that the cooling effect would be 
greatly reduced. It is also evident that more oxygen would reach 
the fuel in given time. We would effect a double gain. That is 
exactly what is done in the oxy-acetylene apparatus. We use 
pure oxygen gas to combine with the combustible gas, and secure 
a flame the hottest part of which, not much larger than a pencil 
ploint, has a temperature that will melt the most refractory 
materials. The torch is capable of producing a very high tem- 
perature in a concentrated flame because the gases used are 
pure oxygen and acetylene. Nothing is supplied that is not re- 



quired for combustion. No ashes are produced and no inert gas 
like nitrogen dilutes the oxygen. The oxygen and acetylene gases 
are supplied from separate sources through hose. The oxygen 
supply comes through the black hose while the acetylene or com- 
bustible is supplied through the red hose. These gases under 
pressure are fed to the torch through the respective hose into the 
handle. Just back of the handle you will find two needle valves. 
The valves are for controlling the flow of the gas and securing the 
proper proportions of oxygen and acetylene supply. 

The two tubes join in the head where the gases are brought 
together and mixed. The amount of gas that can escape at the 
tip depends on the diameter of the hole. The gas flowing from the 
tip governs the size of the flame. If we need a small flame we 
must provide a small hole in the tip and if we need a large flame 
we must have a larger hole. This is taken care of by changing 
the tips to suit the work in hand. The tips are interchangeable 
and are easily removed and replaced by loosening a nut which 
holds them in place. The gases mix in the head of the tip, and 
each size of tip is drilled to secure the most thorough inter- 
mingling of the volume of gas it is designed to supply. The tips 
are numbered, the small tips having the low numbers and the 
large ones the high numbers. The smallest tip is No. 00 and the 
largest No. 12, for the Style C welding torch. The size of the tip 
in this torch is No. 2. 

We open the oxygen cylinder valve and adjust the oxygen 
regulator to a pressure of four or five pounds, with the upper 
needle valve in the torch handle open. Then we close the oxygen 
needle valve in the torch and open the lower or acetylene needle 
valve. The acetylene regulator handle is in the closed position, 
being turned to the left. We open the acetylene cylinder valve 
and adjust the acetylene regulator to a working pressure of two 
pounds. The gas is now flowing from the acetylene cylinder 
through the red hose and escaping from the torch tip. We use 
the ignitor and light. 

You will notice that it burns with a long smoky flame. The 
oxygen required to support combustion now comes from the air 
around it. Now open the oxygen valve, and' notice an immediate 
change. The smoky flame has disappeared, and we have a shorter. 



more fiercely burning flame, the hottest part of which is evidently 
at the tip. By turning the needle valve we change the appearance 
of the flame. When the proportion of oxygen and acetylene are 
exactly right for perfect combustion we have what is called the 
neutral flame. The neutral flame tends neither to carbonize the 
metal against which it is directed, nor to oxidize it. If we shut 
off a part of the oxygen supply you will notice that the flame then 
consists of a white cone, a white envelope verging into a blue 
as it becomes further removed from the tip. When directed 
against metal the free or excess carbon in the flame tends to com- 
bine with the heated metal. This is shown by a cloudy boiling 
in the puddle. This we call a carbonizing flame because it tends 
to increase the carbon content of the metal being welded. If 
now we increase the oxygen supply we notice that sparks fly when 
the flame is directed against the steel. The molten metal foams 
and sparks and burns. We now have an oxidizing flame — an ex- 
cess of oxygen. The excess oxygen tends to burn the steel as 
well as the acetylene. 

In adjusting your torch flame the aim should be to produce 
the neutral flame. You should learn to distinguish between the 
neutral, carbonizing, and oxidizing flames instantly. Much of the 
trouble experienced by oxy-acetylene welders has been due to 
lack of skill in adjusting their torches. Improper adjustment 
means the wrong flame and that means poor welding and wasted 
gases. 

The oxy-acetylene apparatus is flexible; the flame may be 
directed exactly where we want it. Wd take the flame — our 
welding tool — to the work. The blacksmith must take his work 
to the forge and heat it all over. Then he must pound it with a 
hammer. No hammering is required for torch welding. The 
molten metals merge and become one in cooling. The forge is a 
crude primitive means for welding compared to the highly port- 
able, flexible and efficient oxy-acetylene torch. It can be used only 
for welding iron and steel whereas the torch will weld cast iron, 
copper, brass, aluminum and other metals also. 



10 



Questions 

1. What is the effect of an air blast on fire? 
3. Why does the blacksmitli's forge produce a higher tem- 
perature than can be obtained in an open fire? 

3. What gas is the supporter of combustion? 

4. What is welding? 

5. What are the common fuels? 

6. What are the conditions required for perfect com- 
bustion ? 

7. Is a large fire necessarily a hot fire? 

8. What are the colors of the oxygen hose and the acety- 
lene hose? 

9. What do you do when you want to change the size of 
the torch flame? 

10. Which needle valve in the torch do you open first when 
starting ? 

11. Where is the hottest part of a torch flame? ' 

12. What kind of a flame is required for most welding? 



11 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

FLAME AND ITS STRUCTURE 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



FLAME AND ITS STRUCTURE. 

All Flame Combustion Gas Combustion — Structure of Candle Flame — Bunsen Gas 
Burner — Bunsen Burner Embodies Principles of Torch — Carbonizing, Oxidizing 
and Neutral Flame Characteristcs — Adjusting the Torch Flame. 

Combustion is the burning of any fuel with a supply of 
oxygen, taken either from the atmosphere or from some other 
source of oxygen supply. In this lecture we will take up com- 
bustion in the typical flame. The principal combustibles are wood, 
charcoal, hard coal, soft coal, coke, tar, petroleum, fuel oil, kero- 
sene, illuminating gas, hydrogen, and acetylene. You will notice 
that this list includes solids, liquids and gases. 

All Flame Combustion Gas Combustion 

All flame combustion is gas combustion, irrespective of whether 
the fuel is solid, liquid, or gaseous. We have here an ordinary 
paraffine candle. We light the wick. As soon as the wick is afire, 
the heat creates a pool of liquid paraffine around the base of the 
wick. The liquid paraffine rises in the wick by capillary action 
until it reaches the zone of the flame, and there it gasifies and 
burns the same as the gas flame from a gas tip. When coal burns 
in the grate, the action is somewhat different, but the result the 
same. The coal is composed of carbon and hydrocarbons. A 
fire of some easily ignited' material like wood must be built first 
on the grate, and when the wood has become fully ignited a 
small amount of coal is put on at first. The temperature of the 
burning wood is sufficiently high to raise the small amount of 
coal to the igniting point. What does this mean? It means that 
the coal is made so hot by the burning wood that the imprisoned 
gases are released. The escaping gases are combustible, and they 
take fire and continue to burn until the coal is consumed. The 
gases are essentially the same as the gas that comes from a gas 
jet. In fact illuminating gas is manufactured by the distillation 
of hard coal in retorts. It is washed, purified and enriched with 
oil gas before being turned into the street mains. In the case 



of coal the production of gas takes place without melting the 
combustible first, as occurs in the candle, but the chief com- 
bustible is changed to gas in both cases. All combustibles are 
partly or wholly gasified as they burn. It makes no difference 
whether they are paper, wood, oil, tallow or any other solid or 
liquid. The hydrocarbons contained change into the gaseous 
state as they burn. 

Structure of Candle Flame 

Now we will examine the candle flame, and note its structure. 
In the center we have the wick, which serves to draw the liquid 
paraiifine from the pool beneath to the bvirning zone. Surround- 
ing the wick you will note a dark shape or cone. This is the 
gas escaping from the wick. You don't see the gas, but your eyes 
see a dark space where there is no flame and no light emitted. 
Surrounding this dark cone is the bright envelope or flame where 
combustion is actually taking place. Outside this bright envelope 
is another cooler semi-incand'escent envelope. This outer envelope 
has tongues, curves and waves. Its shape is ever-changing. The 
flame is fed by the oxygen from the atmosphere ; as the air rushes 
in from all sides it disturbs the flame, causing it to flicker, wave, 
rise, fall, and perform in the characteristic manner of flames in 
general. Flame then is red-hot and white-hot gas and air. 

The flame is more or less smoky. If we hold this plate over 
the flame it is immediately blackened with soot. The soot is fine 
carbon and is unconsumed fuel. When you see smoke issuing 
from a factory chimney you see finely divided carbon or uncon- 
sumed fuel floating away with the invisible gases. Thousands 
of tons of coal are wasted every year by imperfect combustion, 
always accompanied by smoke. The power house chimney that 
belches smoke is a nuisance to the community and a disgrace to 
the engineer in charge. 

The hollow structure of the flame is shown by a simple ex- 
periment. We insert a match stick in the flame quickly and 
leave it for an instant and remove. You will notice the part of 
the match in the center of the flame is hardly blackened while 
the parts exposed to the edge of the flame are burned. This 
shows that the center of the flame is comparatively cool and that 



the hottest part is in the bright envelope surrounding the dark 
center. 

Bunsen Gas Burner 

Here is a gas burner of the Bunsen type. It consists of a 
short tube mounted in a base and connected to a source of gas 
supply. Near the bottom of the tube is a number of holes through 
which air can enter and mix with the gas. Surrounding this 
part of the tube is a closely fitting ring, also containing holes. 
We can turn this ring so that it wholly or partly closes the air 
holes in the tube. We will turn the ring or shutter so that it 
shuts off all the air and then ignite the gas. The flame burns 
much the same as the candle flame. There is a hollow center 
surrounded by a bright envelope, and around this is the cooler, 
smoky envelope, much like that we saw in the candle flame. We 
place a match stick in this flame and quickly withdraw it. The 
center is unburned but the parts that lie in the envelope are 
charred. The center of this gas flame must be cool because it 
is composed of gas coming up through the pipe. It is not quite 
so plain that the same condition exists in the candle flame, but 
the two experiments show that what is true of one is true of the 
other also. 

We will now turn the shutter ring in the base and admit 
air with the gas. Immediately the appearance of the flame 
changes. The dark center is diminished in size and surrounded 
by a green cone, while above is a blue streamer and outside that 
a pinkish envelope. There are three distinct flame structures 
visible. The cone is not so apparently hollow as before, but it 
still has a core of unburned gas, as may be proved by again 
using the match stick. The stick thrust into the flame is charred 
at the margins of the flame but unblackened at the core. Com- 
bustion is going on quite close to the center, however, as well as 
in the outer envelopes. This is shown by the fact that the stick 
is charred throughout a greater part of the diameter of the flame 
than before. The flame is much hotter in the zone of the blue 
cone than before . 

The experiment shows that combustion in the Bunsen burner 
is different from that of the candle flame when the air is mixed 



with the gas. Why does this make a difference? It is due to 
the fact that when the ring at the base is turned to admit air a 
combustible mixture is produced that burns more or less uni- 
formly throughout as it issues from the pipe. The flame is not 
now dependent on securing a supply of oxygen from the sur- 
rounding air; it finds its oxygen already mixed with the gas 
supply. Combustion, therefore, takes place throughout without 
the flickering and curling noticed when the air, or oxygen supply, 
is fed to the flame from the outside. 

The Bunsen burner demonstrates the advantage of mixing 
the combustible gas and the atmosphere in correct proportions 
for complete combustion before combustion takes place. It 
operates under a disadvantage, however, which is important to 
call to your attention. The air entering the holes in the base of 
the burner is approximately one-fifth oxygen and four-fifths 
nitrogen. The nitrogen is incombustible and acts simply as a 
dilutant. It absorbs heat from the flame and passes away greatly 
expanded, much hotter, but unchanged. It contributes nothing 
to flame temperature, but on the other hand robs the flame of 
heat. 

Bunsen Burner Embodies Principles of Torch 

The Bunsen flame is very hot, but you would not know it 
by the color. We can convert some of the heat into light by 
simply placing over it a Welsbach gas mantle. Immediately we 
have an intense light; the temperature of the flame raises the 
mantle to the incandescent point and the thorium and cerium with 
which it is impregnated throw off a very white light. The Bun- 
sen burner embodies the principle of the oxy-acetylene torch. In 
the torch we have the tip which corresponds to the tube, and the 
head which corresponds to the base containing the holes and the 
air supply control ring or shutter. You do not see this mixing 
part, as it is concealed in the head. The lower tube, the one 
connected to the red hose, supplies the combustible gas, while 
the upper one, connected to the black hose, supplies the oxygen. 
The two gases enter the head separately. They meet in the tip 
head and mix and then escape at the end of the tip, where com- 
bustion takes place. 



The gases supplied to the oxy-acetyJene torch are commer- 
cially pure acetylene and oxygen. The use of pure oxygen greatly 
increases the temperature of combustion, owing to the fact that 
we have eliminated the inert nitrogen, which acts merely as a 
dilutant and robs the flame of heat in the simple Bunsen burner. 
The flame produced with acetylene and oxygen is so hot at the 
tip of the white cone that it will fuse firebrick and make it run 
like water. The zone of the highest temperature is in this white- 
hot cone, and when fusing metals it is held close to the metal but 
not too close for fear of introducing unburned gases into the 
puddle of molten metal. The most effective flame for welding 
is obtained only by careful adjustment of the torch needle valves, 
as will now be explained. 

Carbonizing, Oxidizing and Neutral 
Flame Characteristics 

When we light the torch we light the acetylene gas first. 
The flame that issues is long and smoky, denoting imperfect com- 
bustion. It is curly, it flickers and changes shape. Streamers 
shoot out from the sides. This is caused by the air rushing in 
from all sides to supply the oxygen that supports combustion. 
The oxygen is now derived from the atmosphere. The flame is 
hot but not so hot as it would be if it did not burn smoky. Com- 
bustion is imperfect. 

Now open the oxygen needle valve and note the difference. 
Immediately the flame changes. The smoky condition has dis- 
appeared and a white cone of flame appears at the tip. Sur- 
rounding this white cone — not much larger than a grain of 
wheat — is an envelope of cooler flame. You will notice in the 
center of the white cone, a darker cone denoting the gas issuing 
from the tip. It is comparatively cool. The hottest part of the 
flame is at the point of the white incandescent cone. It is very 
important that you get this clearly in mind, as success or failure 
in welding depends on the application of the flame correctly to 
the part that is to be welded. 

It is evident that we can change the character of the flame 
by opening or shutting these needle valves. If we open the 
acetylene valve and close the oxygen valve the flame burns 



smoky, and the hot cone or flame of greater intensity disappears. 
As we open the oxygen valve the intense flame increases until 
it reaches a maximum. Finally as we open the oxygen valve 
wider, we note a difference in the flame — it roars and burns more 
spitefully. Too much oxygen now is supplied for perfect com- 
bustion. 

Let us try the effect of the different flames on a piece of 
steel. We will first start with an excess of fuel, that is the 
acetylene supply will be in excess of the oxygen supply. When 
this flame is directed against the metal it becomes red, then 
white hot, and then the metal melts and begins to boil. What 
does this boiling indicate? It shows that the flame contains 
excess fuel or carbon. The carbon is mixing or uniting with 
the steel as it melts. The steel is carbonizing, and it will be 
brittle when cold. A flame that causes the steel to boil and 
become cloudy is a carbonizing flame. The resulting weld will 
be pitted and brittle. The carbonizing flame must be carefully 
avoided when welding steel, if you wish to produce sound strong 
welds. A slightly carbonizing flame is recommended for welding 
aluminum. 

Now turn on the oxygen by opening the oxygen needle valve 
further. Adjust the valve so that the carbonizing flame envelope 
just disappears, and no further. The flame now burns clean. 
The white hot cone at the tip is well defined. When we apply 
to it the steel, the metal becomes white hot and melts, but it lies 
quiet under the flame. It neither boils nor sparks. This is the 
neutral flame, and is the flame that you should always try to get 
when welding steel It should be remembered that the so-called 
neutral flame has the neutral characteristic only when properly 
applied to the metal. If held too close the unburned gas in the 
core may penetrate the molten metal and result in producing 
occlusion, blowholes and other defects. 

Note the difference when we open the oxygen valve still 
further. The white cone, or section of intense heat, becomes 
very short, and blue-white. Outside is a long blue envelope. The 
flame roars and sounds spiteful. When this flame is directed' 
against the steel and it reaches the melting temperature the metal 
foams and sparks. This action shows that excessive oxygen is 

8 



being- supplied and that the oxygen is combining with the steel 
and burning it. The oxidizing flame is as fatal to success in 
welding as is the carbonizing flame, and must always be avoided. 
It is shown by foaming and sparking. The resulting weld is 
shiny and weak. 

You now have seen the three conditions of flame ; at the one 
extreme is the smoky carbonizing flame, due to excess fuel; at 
the other is the sparking blue flame, due to excess oxygen; and 
between is the steady flame of greatest intensity. The molten 
metal lies in a clear, clean pool or puddle beneath this flame. It 
tends neither to become cloudy and boil nor to foam and spark. 
You will fail as a welder if you do not become proficient in 
adjusting the flame to secure neutral or balanced' combustion. 
Balanced combustion is desirable not only because it produces the 
best welds, but because it makes for economy of gas consumption. 
When you burn a carbonizing flame you are wasting acetylene; 
and when you burn an oxidizing flame you are wasting oxygen. 
It is only when you have the perfectly balanced flame that you 
are burning both gases economically. So, from every point of 
view it is necessary to adjust the flow of gases carefully and 
secure the neutral flame to get the best results. 

Adjusting the Torch Flame 

Four distinct flames can be produced with the oxy-acetylene 
torch, but three, only, produce sufficient heat for welding iron 
and steel. A in Fig. 1 shows the pure acetylene flame. The gas 
is burning with no oxygen supply except that which comes to it 
from the atmosphere. A short gap appears between the tip and 
the flame. B shows the carbonizing flame. The acetylene 
is burning with partial but insufficient oxygen supply. E 
shows the balanced or neutral flame. This is the correct 
flame to use. The oxygen and acetylene are supplied in exactly 
the right proportions for efficient combustion. D is the 
oxidizing flame. More oxygen is being supplied than required 
for the burning of acetylene. 

Carbonizing Flame Characteristics 

Combustion is unbalanced ; there is insufficient oxygen and 
excess carbon in the flame. A white cone appears at the tip, and 



beyond the flame there is a white envelope of cooler flame. The 
streamer is a long blue flame. 

Effect of Carbonizing Flame. — The excess carbon tends 
to enter and combine with the molten metal. The metal boils and 
has a cloudy appearance. The surface of the weld when cool 
is mottled or pitted in appearance. The weld is brittle. 

Neutral Flame Characteristics 

Combustion in the flame is balanced, and two distinct cones 
are visible. The cone next to the tip is white hot, and beyond 
it is a long blue streamer, also very hot. The sound of the 
neutral flame differs from that of the carbonizing flame. 

Effect of Neutral Flame. — The molten metal lies quiet 
beneath the flame. It is clean and clear. It flows like syrup, 
and few sparks are produced. The weld made with the neutral 
flame will be free of carbonized and oxidized metal. 

Oxidizing Flame Characteristics 

Combustion is unbalanced because of excess of oxygen. The 
oxygen combines with all the fuel or acetylene available, and the 
remainder tends to attack the metal. The white cone is very 
short and is surrounded by a blue white envelope. The streamer 
of the flame is blue. 

Effect of Oxidizing Flame. — The metal sparks, and a 
white foam forms on the surface of the puddle, denoting oxida- 
tion. The cold weld is shiny and has little strength. It contains 
oxidized metal. 

Summary 

The carbonizing flame is caused by excess acetylene gas ; its 
effect is to make a brittle weld. The oxidizing flame is caused by 
excess oxygen; and its effect is to make a shiny weld of little 
strength. The neutral flame is produced by balancing the oxygen 
and gas supply so that perfect combustion is secured. Excess 
of either gas is harmful and wasteful. The welds produced with 
the neutral flame are sound and free from oxide and excess 
carbon. 

10 



Questions 



1. In what way do you determine the neutral or balanced 
flame? 

2. Why does the combustion of oxygen and acetylene pro- 
duce so hot a flame? 

3. Which is the combustible gas? 

4. What part does oxygen play? 

5. What is the appearance of an oxidizing flame? 

6. What is the appearance of a carbonizing flame? 

. 7. How do you know when you have the neutral or bal- 
anced flame? 

8. What is the appearance of a weld made with a carbon- 
izing flame ? 

9. What is the appearance of a weld made with an oxidizing 
flame ? 

10. What part of the flame is the hottest? 

11. How close should the flame be held to the metal? 

12. Why should care be taken not to touch the metal with 
the white hot cone? 



11 



Copyright 1919 by the 
Davis-Bournonville Company 



DAVIS-BOURNONVILLE 

OXY-ACETYLEINE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



REGULATING THE GAS 
SUPPLY 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 




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REGULATING THE GAS SUPPLY 

All Gases Compressible — Pressure Reducers or Regulators— ^To Regulate 
Working Pressure — Principle of Pressure Gauge Operation — Danger of Testing 
Oxygen Gauges with Oil — Pressure Reducers or Regulators — Principle of Pressure 
Regulator Action — Direct Acting Pressure Regulator — Line Pressure Regulator of 
the Indirect-Acting Type — Care of Regulators — Action of Pressure Regulators 
Reviewed. 

In the previous lecture we talked about combustion and the 
structure of flame. Today we will take up the matter of 
controlling the flow of the oxygen and acetylene gas to the torch. 
The flow of gas through a pipe depends on the diameter of the 
pipe and the pressure behind it. If you need little gas a small 
pipe and low pressure will supply it, but if you need much gas 
for a large flame a larger aperture and greater pressure will be 
required. The control of the torch flame then is accomplished 
by regulating the size of the orifice through which it escapes to 
the atmosphere and the pressure of the respective gases. This 
talk will be on regulating the gas pressures. 

All Gases Compressible 

You have noticed, of course, that the hose are connected to 
two pipe-lines or sources of supply. In the field your sources 
of gas supply will be usually two cylinders like these ; one of the 
cylinders contains the fuel supply or acetylene gas, and the other 
the oxygen. The gases in the cylinders are condensed under heavy 
pressure. All- gases are compressible, which means, for instance, 
that a gallon of gas may be squeezed into a half-gallon can if 
sufficient pressure is applied. There is, in fact, hardly any limit 
to the compressibility of gases in general. Gas is quite different 
from water in this respect. A gallon of water is a gallon — no 
more and no less. Practically you cannot squeeze it into much 
less space, no matter how great the pressure applied. A pressure 
of 3000 pounds to the square inch will compress water only one 
per cent. A pressure of 3000 pounds to the square inch will 
compressure gas into less than one-two hundreth of its free bulk. 
The oxygen cylinder contains the gas under a pressure of about 



1800 to 2000 pounds to the square inch, while the acetylene 
cylinder contains this gas under a pressure of about 225 pounds 
to 275 pounds to the square inch. These pressures are the maxi- 
mum, and they decrease as the gases are used. 

Pressure Reducers or Regulators 

You will notice on the oxygen cylinder two gauges, and 
below one of the gauges a device called the gas pressure regu- 
lator. This gauge, which registers up to 3000 pounds per square 
inch, shows the pressure of oxygen in the cylinder when the stop 



ADJUSTING SCREW 



WORKING PRESSURE 
GAUGE 




Djvis Bournonville Institute 



FIG. 2. DIAGRAM SHOWING PRINCIPLE OF SIMPLE PRESSURE 
REGULATOR, AND PRESSURE GAUGE. 

valve is open. We cannot use a pressure of 1800 pounds to the 
square inch in the torch ; it is entirely too high, and must be re- 
duced to a comparatively low working pressure. The working 
pressure depends on the aperture in the tip, which in turn 
governs the size of the flame. For welding metals up to }i inch 
thick the acetylene working pressure is the same as the number 
of the tip and two times the number of the tip for the oxygen. 



For instance, if a No. 2 tip is being used we should adjust for a 
working pressure of two pounds acetylene and four pounds 
oxygen per square inch. To regulate the gas supply proceed as 
follows, first making sure that the regulator handles are in the 
closed position : 

To Regulate Working Pressure 

Open the valve on the oxygen cylinder as far as it will go, 
and admit the gas to the pressure regulator. This Stop valve must 
be opened very slowly as you are dealing with a very heavy 
pressure, which will surely damage the apparatus if not handled 
carefully. The valve must be opened wide in order to prevent 
leakage around the stem. You will note that as the gas was 
admitted the hand on the gauge has moved from the zero point. 
It now indicates about 1800 pounds pressure. Having turned on 
the oxygen we are ready to adjust the working pressure by 
means of the pressure regulator. To do this open the oxygen 
needle valve in the torch and turn the regulator valve handle slow- 
ly to the right. At first it moves easily and then it begins to offer 
some resistance. When you feel the resistance increasing, turn 
the handle slowly. Now the gas is escaping through the hose. 
The hand of the working gauge begins to move over the gradu- 
ated dial, and when it reaches 4 stop opening the regulator valve. 
The flow of gas has been adjusted for a working pressure of four 
pounds per square inch, which is about right for the No. 2 tip 
when the gas supply is constant. If, however, the supply is taken 
from a cylinder it is customary to adjust for slightly higher work- 
ing pressures in order to compensate for falling pressure as the gas 
is used up. 

Now close the oxygen needle valve in the torch, and open the 
acetylene needle valve. Open the stop valve on the acetylene 
cylinder also very slowly. The pressure on the gauge rises to 
about 225 pounds per square inch. Having admitted the acetylene 
to its pressure regulator we are ready to regulate the working 
pressure of the fuel supply. Turn the regulator handle to the 
right slowly as before, until it meets increasing resistance, and 
then turn very slowly. As the valve opens and admits the 
acetylene gas the hand of the acetylene gauge begins to move 



over the graduated dial and when it indicates 2, or slightly more, 
stop opening the regulator. Close the acetylene needle valve if 
not ready to immediately ignite the flame. As a rule you should 
be ready to start using the torch, but we will close the acetylene 
valve for the moment, and describe the construction of the gauges 
and the regulators. It is important that you understand' the 
principles of these parts of the apparatus, as your success as a 
welder and your personal safety depend on the care you give 
them. 

Principle of Pressure Gauge Operation 

Here is a pressure gauge that has been partly dismantled to 
show the construction. You notice in the center, a curved flat 
tube, one end of which is attached to the gauge stem, while the 
other or closed end is connected by means of a lever and a short 
curved rack to a small pinion. 

We will mount this gauge on the cylinder and open the valve. 
The tube tends to straighten when the pressure is admitted, but 
the movement is too small to be seen. It is known as a Bourdon 
tube, and is the pressure part generally used in gauges. A tube 
like this tends to straighten when subjected to internal pressure, 
because the flattened cross section tends to become circular. This 
has the same effect as increasing the inner circumference and 
shortening the outer. The movement of the end of the tube is 
so slight that it is necessary to multiply it in order to see the 
movement of the hand on the dial. This multiplication of move- 
ment is accomplished by the lever connection and the curved rack 
and pinion. The pinion is mounted on the spindle that carries 
the indicator hand. A very small movement of the tube will turn 
the hand completely around the dial. Beside the pinion is a hair- 
spring; one end is attached to the body and the other to the 
spindle. This hairspring offers a slight resistance to the move- 
ment of the Bourdon tube, and it returns the hand to the zero 
point when the pressure is released. 

The movement of the hand over the graduations of the dial 
is calibrated or compared with a master gauge to make sure that 
the indications represent correctly the pressure in pounds per 
square inch. The term "pounds per square inch" means that 



every square inch in the cyhnd'er shell supports a load, pressure, 
or weight, and a gauge pressure is a device for weighing the 
pressure. If the internal area of the shell of an oxygen cylinder, 
for instance, is 100 square inches, it sustains a load of 180,000 
pounds when the pressure is 1800 pounds to the square inch. 

The outer graduations on the high pressure oxygen cylinder 
gauge dial read "Pounds per Square Inch in the Cylinder;" the 




IT 



Davis Bournonvllle Institute 



FIG. 3. DAVIS-BOURNONVILLE NO. 2 HIGH-PRESSURE OXYGEN 

REGULATOR. 

graduations of the next circle read "Number of Cubic Feet in a 
100-Foot Cylinder ;" and the inner circle of graduations "Number 
of Cubic Feet in a 250-Foot Cylinder." Thus, you can tell at a 
glance both the pressure and the cubic feet remaining in a 100- 
foot or 250-foot cylinder. If you have a 200-foot cylinder you 
simply double the reading for a corresponding pressure in a 100- 
foot cylinder. 



The front of the gauge is covered with thick glass. This 
glass is to protect the hand and the dial from mechanical injury 
and corrosion. A metal diaphragm is provided between the dial 
and the works, and the back of the gauge is loosely fastened in. 
The reason for this construction is that we are dealing with 
very heavy pressures and a delicate apparatus. The Bourdon tube 
must necessarily be made of thin metal in order to be flexible. 
Sometimes the metal in the tube cracks. If this should happen 
the oxygen gas at a pressure of pejhaps 1800 pounds to the 
square inch would escape into the gauge case, and explode it. 
If the back was firmly fastened and no diaphragm was pro- 
vided, the front or glass part would be blown out, the flying 
splinters of the glass might seriously cut anyone standing nearby 
or destroy the sight of the eyes. It is better then to let the 
back blow out in case of accident, as this being metal will not 
shatter. When the back is blown out the pressure is relieved 
and there is no danger then of the glass breaking. The safest 
position to take when opening a cylinder stop valve is in front of 
the dial. 

Danger of Testing Oxygen Gauges with Oil 

In the early days of the industry it was quite a common 
experience to have the high-pressure gauge upon the oxygen regu- 
lator explode. Sometimes the operator was not injured and some- 
times he was badly hurt. Usually the reason for gauge explosions 
was the fact that users did not understand that oil and oxygen 
might cause trouble and the gauges were tested upon an oil gauge 
testing machine, which was a common piece of apparatus in the 
ordinary shop. The Bourdon tube of the gauge was filled with 
oil during the test, and then the gauge was directly screwed into 
the regulator without removing the oil. Nowadays oil is not used 
in testing gauges because practically all gauge manufacturers 
appreciate the risk run in so doing. The best practice is always 
to test the gauge with water and never with oil. 

The same remarks do not apply to acetylene or hydrogen 
gauges and regulators because acetylene and oil or hydrogen 
and oil do not form an explosive mixture, but it is good practice 
to avoid the use of oil in connection with all regulators, cylinder 



valves, etc. Soir.eone wlio does not know the difference may 
see oil upon an acetylene regulator and believe that it would 
work equally well in connection with oxygen. 

The principle of the low pressure working gauge is prac- 
tically the same as that of the high pressure gauge, but as it is 
intended for lower pressure, it is not so strongly made. No 
diaphragm is provided and no provision is made for letting the 
tack blow out, as these precautions are unnecessary. 




SAFETY DISK 



Davis Sournonville li>st{tute 



FIG. 4. HIGH PRESSURE AND WORKING PRESSURE GAUGES AND 
PRESSURE REGULATOR FOR OXYGEN CYLINDER. 

Pressure Reducers or Regulators 

We will now give attention to the gas pressure regulator. This 
is a highly sensitive apparatus that has required, perhaps, as much 
thought to perfect its design as any other part of gas welding 
equipment. The design of the regulator is important because it 



should function properly at all times and under widely varying- 
conditions. If the regulator does not regulate you might as well 
give up trying to weld because perfect regulation is absolutely 
necessary for success. Choose your regulator with understand- 
ing of its function, design and construction. Take the best care 
of it possible but, remember, that like all sensitive apparatus 
it may get out of order and require readjustment with even the 
best of care. 

You can regulate pressure in a steam radiator by opening 
the valve a little way when you do not want the full pressure. 
The steam in a radiator condenses as fast as it enters, and the 
pressure remains nearly constant. But if you undertook to regu- 
late the pressure in an air container in the same manner by 
opening a compressed air valve connected to it a fraction of a 
turn, you would not be successful. The pressure would "build 
up" in the container and soon reach the same figure as in the 
source of supply. It is necessary, then, to provide an apparatus 
that definitely measures ofif a certain flow of gas and checks the 
flow as soon as the pressure on the low side has reached a pre- 
determined figure no matter what it may be. The gas regulator 
does this automatically when properly made and adjusted. 

Principle of Pressure Regulator Action 

The diagram, Fig. 1, is intended merely to show the princi- 
ple of operation of the primitive or simple form of pressure 
regulator. It is not the regulator that you use, but its general 
principles are the same. The diagram shows the connection 
of the regulator to the high pressure oxygen supply. At A is 
the cylinder stop valve and at B the cylinder pressure gauge, at 
C the regulator and at D the working pressure gauge. The high 
pressure oxygen cylinder is at 0. The pressure in this tank when 
received from the manufacturer is about 1800 to 2000 pounds, 
and it must be reduced to a working pressure of say ten pounds 
to be used in the torch. 

The regulator case is in two parts, and between them is a 
thin metal or rubber diaphragm F. Connected to the diaphragm 
beneath is a stirrup-shaped part or yoke terminating in a flat 
valve, disc G. This covers the opening in the high pressure 

10 



oxygen supply nozzle. Above the diaphragm is a coil spring, H, 
seated between the diaphragm and end of the regulator screw, I. 

The diaphragm normally holds the valve disc, G, up against 
the nozzle, and shuts off the oxygen from entering the lower 
chamber. But when you adjust the gas regulator to get the 
desired working pressure you screw I to the right, thereby com- 
pressing the spring H and pushing down the diaphragm. This 
forces the valve away from its seat and permits the high pressure 
oxygen to enter the chamber and escape through the hose to the 
torch. When the oxygen at high pressure enters the lower cham- 
ber, it exerts pressure on the lower side of the diaphragm and 
tends to close the valve and shut itself off. The operation of 
setting the regulator is one of compressing the coil spring until 
it balances the working pressure desired. Your guide is the 
working pressure gauge D, mounted on the outlet to the torch. 
The diagram should serve only to give you an idea of the princi- 
ple of regulator operation. Do not imagine that it truly represents 
the actual construction of an up-to-date and reliable gas regulator. 

There are several types of regulators all operating upon the 
same general principle but differing in design. These types may 
be classed as direct-acting and indirect-acting regulators. 

Direct Acting Pressure Regulator 

An example of the direct-acting gas regulator is the Davis- 
Bournonville No. 2 high pressure oxygen regulator shown in 
Fig. 2. The construction and operation are quite similar to that of 
the diagrammatic form shown In Fig. 1. Gas under liigh pressure 
enters through the inlet A to E, where the gas passage turns 
downward and terminates in a screwed nozzle, L. Straddling E 
and the nozzle is a bronze loop or stirrup, M, attached at the 
upper end by a hook to the diaphragm F, and carrying below the 
valve disc G. The disc is held in a pocket in the bottom of the 
stirrup, and is supported by the pivot pin N. 

The diaphragm H when not forced down by the coil spring 
I tends to pull the stirrup or yoke up and holds the valve disc 
tightly against the flat end of the nozzle L. When the valve 
disc is against its seat no gas can pass from A into the chamber 
K through the nozzle L. To permit the gas to flow the screw I 

11 



is turned to the right, thus compressing the coil spring H, which 
in turn forces the diaphragm down and unseats the valve disc. 
The gas then escapes into chamber K and thence to the outlet P, 
Fig. 3. This direct-acting regulator provides an auxiliary spring; 
R beneath the stirrup to hold it aganist the seat when the dia- 
phragm is relaxed. 

The gas in chamber K presses upward on the diaphragm and 
counterbalances the pressure of the coil spring H. The adjust- 
ment of the regulator then is a matter of compressing the spring 
by the screw until its pressure is approximately equal to the 
pressure of the gas in pounds per square inch multiplied by the 
area of the diaphragm in square inches. 

Line Pressure Regulator of the Indirect- Acting Type 

Fig. 3 shows the Davis-Bournonville acetylene pressure 
regulator of the indirect or lever type for regulating the pressure 
in supply lines. The lever connection between the diaphragm 
and the inlet valve is so proportioned that the diaphragm end 
moves about three times as far as the short end controlling the 
movement of the valve. Thus a movement of the diaphragm 
center of say one-hundreth inch is reproduced at the gas valve 
by a movement of only about one three-hundreth inch. The 
design thus provides a reducing movement by which the opening 
of the gas valve may be controlled with very small variations. 
The regulator shown is for operating under the low pressure of 
15 pounds per square inch and reducing it to the torch working 
pressure. The same general design is also provided for oxygen 
pipe line pressure control. 

The inlet A is connected to the pipe line, and the gas passes 
through a screen or strainer and beneath the valve disc G into 
the cavity K, where it exerts pressure on the diaphragm F, as 
in all the other types of pressure regulators. The outlet P to the 
torch is in direct line with the inlet passage. 

Pressure regulation is effected by means of the regulator 
handle I and the compression spring H, which must be adjusted 
so that the pressure of the spring on top of the diaphragm 
counterbalances the gas pressure beneath and also the pressure 
exerted by the auxiliary regulator spring Q seated on the 

12 



auxiliary diaphragm S. Beneath this diaphragm is a space con- 
nected by a passage to the gas supply pipe. The coil spring T 
beneath the diaphragm is provided to balance the pressure of 
spring Q and relieve the diaphragm S. The function of the 



2 PLY FABRIC 
RUBBER DIAPHRAGM 




ALL BRASS PARTS TO BE NICKEL PLATED 
EELOA/ MAIN DIAPHRAGM 



s Beurnonville Institute 



FIG. 5. DAVIS-BOURNONVILLE LOW PRESSURE ACETYLENE 
PRESSURE REGULATOR 

supplementary diaphragm is two-fold: It increases the sensi- 
tiveness of regulator action on a pipe line distributing system 
by acting on the valve control level direct. Fluctuations of 
pressure are in a sense anticipated and provided for before the 
change of pressure has affected the pressure in the chamber 
beneath the main diaphragm. It also provides for automatically 



13 



shutting off the flow of gas in case the diaphragm is burst by 
over-pressure. The escape of gas from the chamber K through 
rupture of the diaphragm permits the gas beneath the supple- 
mentary diaphragm and the spring pressure to act on the re- 
ducing lever U in opposition to the pressure of spring H and 
close the valve G firmly upon its seat. The oxygen regulator 
of the same type is provided with a bursting disc beneath the 
supplementary diaphragm to prevent the building up of dan- 
gerous pressures in the line. 

Care of Regulators 

The gas passes through the screen chamber of the regulator 
and is strained by a fine mesh screen before coming in contact 
with the seat. The seat rnust be tight or the regulator will give 
all sorts of trouble. A small particle of scale, grit or dirt lodging 
under the seat will of course make it leak. It can be readily ap- 
preciated that the regulator will not give close regulation and may 
in fact become very troublesome if its use is continued with a 
leaky seat. The pressure upon the diaphragm in that event does 
not shut off the nozzle completely and the gas continues to 
flow into the regulator causing the pressure within the low 
the flow into the regulator causing the pressure within the low 
pressure chamber of the regulator to climb or build. This is in- 
dicated by the small gauge. 

The pressure creeps higher and higher when the torch is 
shut off until finally the small gauge is broken or the safety disc 
in the back of the regulator bursts. This safety disc is a simple 
disc held in position over an outlet of predetermined size by a nut. 
The thickness of the disc and the size of the outlet determines 
the pressure at which it will burst. This pressure is usually some- 
what greater than the maximum working pressure of the regu- 
lator. It will be appreciated, however, that there is a good deal 
of variance in the pressure at which the disc will burst even with 
discs of the same thickness and outlets of the same diameter ; 
hence, the function of the bursting disc is largely to prevent ex- 
cessive pressure remaining long within the regulator casing. The 
disc will burst long before the casings are blown apart but not 
always before serious damage is done to the gauge. 

14 



If a regulator leaks, stop using it and see that it is properly 
repaired before attempting to operate it again. It is not dififir- 
cult to repair the regulator; as a rule, it is only necessary to 
renew the seat and consequently a few extra seats should al- 
ways be available. It is always good practice to maintain a few 
extra bursting discs so that in case one bursts a new one can 
be inserted. It should be borne in mind, however, that if the 
safety disc bursts, you should always test the seat to de- 
termine that it is tight before putting a new disc in place. A 
bursting disc is almost always an indication of trouble elsewhere 
in the regulator. 

In setting up the joint in the regulator, a little shellac is 
usually the best material to use. Do not use paint, white lead or 
oil. High pressure oxygen and oil or any other inflammable 
material are likely to cause an explosion under certain con- 
ditions if confined together. A word should here be said' in 
this connection about the use of a suitable lubricant upon the 
adjusting screw of the regulator. The regulating screw of 
the regulator does not come in contact with oxygen or the gas 
within the regulator as the gas does not pass the diaphragm. 
There is then no reason why a suitable lubricant should not be 
used upon this screw. Care should be taken, however, that 
this lubricant is not allowed to get into the regulator ; it is 
best in such instances to use tallow or graphite and not oil. 

Action of Pressure Regulators Reviewed 

Now to review the action of a gas pressure regulator. When 
the cylinder valve is opened, gas is admitted to the chamber 
communicating with the high pressure gauge but it can go no 
further so long as the pressure regulator handle I is in the re- 
leased position. But when you turn the regulator handle to the 
right or in a clockwise direction it screws in and compresses 
the coil spring directly beyond it. The pressure of the spring 
is transmitted to the diaphragm and the resulting movements 
communicated to the valve stirrup or connecting lever, (de- 
pending on the type of regulator) opens the gas valve and lets 
the gas escape into the chamber beneath the diaphragm. The 
pressure immediately overcomes the pressure of the spring, and 

15 



more clockwise mbvemenf of the regulator handle is required 
to compress the spring still further in order to counterbalance 
the gas pressure. Finally you secure the adjustment required. 
By the process of adjustment you produce a state of balance 
between the pressure of the coil spring on top of the diaphragm 
and the gas beneath it. As soon as the conditions one way 
or another change, the diaphragm rises or falls and the rate 
of flow of the gas escaping from the cylinder is changed. 

Obviously, you cannot adjust a pressure regulator cor- 
rectly unless the needle valve in the torch is open. If you 
want the working gauge hand to stand at 8 pounds pressure 
when the torch is in use the needle valve must be opened while 
you adjust the regulator handle until the hand shows 8 pounds 
pressure. If you undertook to adjust the regulator with the 
needle valve closed the chamber beneath the diaphragm would 
quickly fill and the working pressure indicated would not be 
maintained when using the torch. The moment you opened the 
needle valve it would probably fall below the working pressure 
desired, and thus make necessary readjustment of the regu- 
lator valve handle. ■ 



Copyright 1919 by thk 
Davis- RouRNONViLLE Company 



16 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

THE OXY-ACETYLENE TORCH 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



THE OXY-ACETYLENE TORCH 

The Simple Blowpipe — The Bunsen Burner — The Bunsen Type Blow Torch — 
The Injector Type Blowpipe — Acetylene Commercial Development — Oxygen Com- 
mercial Development — Davis-Bournonville Oxy-Acetylene Welding Torch — The 
Interchangeable Tip System — The Mixing Head or Carburetor — Gas Pressures for 
Welding — Care of Torch and Tips. 

The hand oxy-acetylene torch in general use today for weld- 
ing is a tool or apparatus for mixing a combustible gas with 




FIG. 2. THE SIMPLE ALCOHOL FLAME BLOWPIPE, THE SIMPLE 

BUNSEN BURNER AND THE SIMPLE BUNSEN BLOWTORCH. 



oxygen in certain definite proportions, burning the resulting 
mixture and directing the intensely hot flame upon the parts 
to be welded. 



The Simple Blowpipe 

The gas welding torch is a comparatively recent develop- 
ment of the simple blowpipe that you have often seen used, no 
doubt, by jewelers and watch-makers. Blow-pipes have been 
used from time immemorial by the workers of gold, silver 
and brass to melt their solders and brazes. The ordinary blow- 
pipe is a simple tube curved at the tip through which the 
workman blows against the flame to increase its intensity. It 
is generally used with an alcohol lamp both to increase the 
heat of the flame and to direct the flame point where it is re- 
quired to heat. A skillful workman can direct the flame with 
great precision, and make it melt any of the hard solders. 

The blow-pipe probably antedates the blacksmith's forge. 
It corresponds to the bellows and is a much simpler means of 
producing a blast of air. The first blow-pipe, no doubt, was 
a hollow reed that some primeval man used with astonishing 
effect on a fire and the bits of virgin metal that he had 
collected. 

The Bunsen Burner 

Following long after the Iblow-pipe came the Bunsen 
burner or gas torch. This, like some other very valuable de- 
vices, had its origin in the laboratory. The Bunsen burner 
differs from the blow-pipe in that the air required to increase 
the intensity of combustion is so applied that it mixes with 
the gas before it reaches the zone of combustion. The air Is 
introduced through a tube at the base of the burner where it 
mixes with the combustible gas, and the mixture burns at the 
mouth of the tube with an intense blue flame. 

The temperature of the flame in the simple Bunsen burner 
depends on the gases used and their pressure. The proper 
mixture of air and gas is obtained by adjusting the ring at 
the base which acts like a stove damper. When the ring is 
set so that the openings in the ring and tube coincide the 
maximum amount of air is admitted. Bunsen burners of the 
simple air induction type are generally made so that an excess 
of air is admitted when the ring is adjusted for the full 
opening. 



The Bunsen Type Blow-Torch 

The Bunsen burner we have here is a laboratory apparatus 
of the simple so-called air induction form to demonstrate the 
principles of combustion. It differs from the commercial Bunsen 
burner considerably. Brazing burners or torches are generally 
made so that they may be conveniently handled and usually 
the air is supplied through a separate hose under some pres- 
sure. The Bunsen burner referred to consists of two brass 
tubes united by a cross tube set at a convenient angle, and 
terminating in a nozzle. At the rear are two stop valves by 
which the workman can adjust the flow of air and gas and 
secure the size of flame desired. It is a very simple apparatus, 




ACETYLENE 




MEDIUM PRESSURE 



Davis Bournonville Institute 



FIG. 3. .SECTIONS OF POSITIVE PRESSURE AND INJECTOR TYPE 

TORCH HEADS. 

and is much used for heating, soldering, sweating, brazing, lead 
burning and other purposes where it is necessary to apply heat 



locally. When used for lead burning, the Bunsen burner is 
supplied with pure hydrogen gas and compressed air. In the 
hands of a skilled lead burner it becomes a most eiifective tool 
for uniting the lead sheets of acid tanks. This work, by the 
way, is a form of so-called autogenous welding that has been 
long in use but which is well known to but comparatively few. 
It is rather curious to find that all the elements apparently 
of the modern gas torch were in use years ago; why then has 
it remained for the extraordinary development of the oxy- 
acetylene torch to take place in the past fifteen years? The 
answer is acetylene and oxygen. 

Acetylene Commercial Development 

The discovery of a commercial method of making calcium 
carbide and producing acetylene by Thomas L. Willson in 
1892 gave the world a new combustible of extraordinary char- 
acteristics and value. The commercial possibilities of acety- 
lene made by slacking calcium carbide were early recognized in 
the lighting field but its value as a gas for producing intense 
combustion was not recognized so soon and it was nine years 




FIG. 4. SMALL STYLE C WELDING TORCH WITH REMOVABLE 

INTERCHANGEABLE TIPS. 



later before the first practical oxy-acetylene welding torch was 
developed by Edmund Fouche of Paris in 1901. 

The oxy-acetylene torch is another example of valuable com- 
mercial apparatus that has been m.ade possible by different re- 
searches and discoveries seemingly far apart but which later 



were combined with astonishing success. It had long been 
known that pure hydrogen and pure oxygen burned in the 
Bunsen burner in the proportions of two parts of hydrogen to 
one of oxygen produced an intensly hot flame. The tempera- 
ture produced by the oxy-hydrogen flame is 4000 degrees F. 
It was for many years the source of the greatest flame intensity 
within the reach of the chemist and physicist. 

The first oxy-acetylene torches made by Fouche were very 
crude affairs compared with the modern welding torch 
equipped with its interchangeable tips and efficient gas regulat- 
ing system. Simple and crude as it was it represented tre- 
mendous steps in the advancement of science. Beginning with 
the blow-pipe as a means of increasing the intensity of flame 
the next step was the simple Bunsen burner, burning hydrogen 
and air. The next step of refinement was the burning of 
hydrogen and pure oxygen. This, step was a very important 
one as a supply of pure oxygen will greatly increase the in- 
tensity of any flame. But the next step in the development of 
the oxy-acetylene torch could not be taken as acetylene gas 
was not available. But, when Willson discovered acetylene, 




FIG. 5. SHOWING HOW GASES MAY PASS THROUGH MIXING 

TUBE WITHOUT MIXING IF NOT BROKEN UP. 



then Fouche could develop his torch. The development of 
the liquid air process of deriving oxygen from the atmosphere 
a few years later completed a cycle of discovery which made 
possible a great commercial development. It has transformed 
the old art of welding and made it one of the most advanced 
methods of fabrication. ■ ■ 

The Davis-Bournonville Oxy-Acetylene 
Welding Torch 

We have in the foregoing tried to give you an idea of the 
importance of the oxy-acetylene torch development and what it 
has meant from scientific standpoint. The first oxy-acetylene 
torches used in this country were introduced by Mr. Eugene 
Bournonville, formerly of the Davis-Bournonville Company, 
and Mr. Augustine Davis, president of the company, was one 
of the chief pioneers in its commercial development. 

Here is a Davis-Bournonville oxy-acetylene welding torch. 
It is a simple device, consisting of a handle, two needle valves, 
two tubes for the oxygen and acetylene, head and tip. The 
tubes are silver soldered in the head and fixed in the handle 
so as to give them stability and strength. The head is made 
with a conical seat and is threaded at the mouth for a nut 
which holds a tip with a conical head in position. The upper 
tube is connected to the oxygen supply as you will see by 
tracing the black hose to the oxygen cylinder. The lower 
tube is joined to the acetylene cylinder by the red hose. 

The Interchangeable Tip System 

One of the very important and valuable features of the 
Davis-Bournonville torch is the system of interchangeable tips. 
There are many styles and sizes of interchangeable tips pro- 
vided for this torch, all of which designed for a given size of 
torch may be used in the same torch head at will. Hence, you 
have the means of producing many sizes of flames from the 
smallest to the largest required in commercial welding for 
which a given style of torch is adapted. 

The choice of tip is very important as the size of flame 



should be proportional to the thickness of material to be 
welded and as the size of flame is governed by the size of tip, 
you must consult the table giving the sizes of tips for various 
thicknesses of metal until you become so familiar with torch 
practice that you will instinctively use the right size tip. 

The Mixing Head or Carburetor 




FIG. 6. LARGE STYLE C WELDING TORCH AND TIPS. 

The intimate mixing of the acetylene and oxygen gases is 
accomplished in the conical end of the tip where it fits into the 
torch head. This part is identical in function with the car- 
buretor of a gas engine of a motor car. The carburetor pro- 
vides for mixing a certain definite amount of air with the 
vaporized gasoline thus forming a combustible and explosive 
mixture. The carburetor in the torch tip is the mixing cham- 
ber where the oxygen flowing longitudinally through the tip 
meets the cross currents of acetylene gas flowing in through 
the holes in the sides. The cross currents form a vortex or 
whirlpool, mix and flow through the longitudinal passage to 
the end of the tip where they burn. 

The diameter of the holes in the tip and the pressures of 
the respective gases determine the quality of the mixture. The 
diameters of the holes are graded, and the tips are numbered to 
correspond. A low number tip means small diameter gas pas- 
sages and a small flame suitable for welding thin metal, where- 
as a high number tip means comparatively large gas passages 
and a large flame suitable for welding thicker metal. The 



following table compiled by the Davis-Bournonville Company- 
represents the result of years of experience in welding practice. 

Acetylene and Oxygen Pressures 

Davis-Bournonville Style C Welding Torches 

with Style 99 and 100 Tips 





Thickness 


Acetylene 


Oxygen 


Acetylene* 


Oxygen* 


Tip 


of Metal 


Pressure 


Pressure 


Consumption 


Consumption 


No. 


Inches 


Lbs. 


Lbs. 


Per Hour 


Per Hour 


00 


/Veryl 
iLight/ 


1 


1 


0.6 CU. ft. 


0.8 CU. ft. 





1 


2 


1.0 


1.3 


1 


32 16 


1 


2 


3.2 


3.7 


2 


J 3_ 

16 32 


2 


4 


4.8 


5.5 


3 


A-H 


3 


6 


8.1 


9.3 


4 


li-% 


4 


8 


12.5 


14.3 


5 


K-A 


5- 


10 


17.8 


21.3 


6 


^-% 


6 


12 


25.0 


28.5 


7 


i-,-y2 


6 


14 


33.2 


37.9 


8 


Vi-y^ 


6 


16 


42.0 


47.9 


9 


%-% 


6 


18 


58.0 


65.9 


10 


/4-up 


6 


20 


82.5 


94.0 


11 


r Extra \ 


8 


22 


89.0 


101.2 


12 


1 Heavy/ 


8 


24 


114.5 


130.5 



Operators frequently adjust the pressure regulators from one to two pounds 
above the figures given in the table to allow for gauge variations and drop of pressure 
when the gases are supplied in cylinders. 

* Gas consumption per hour is the maximum with torch burning continuously. 



This table gives the tip number, the thickness of metal for 
which it is suited, the acetylene pressure and the oxygen 
pressure and the hourly consumption of each gas when torch 
is used continuously. 

The No. 00 tip should be used in the Small Style C 
torch for welding metals of the thinnest gauges only. It 
uses very little gas and the regulators should be set for one 
pound per square inch acetylene pressure and one pound 
oxygen pressure. The next tip is No. 0. This also is used 
only on very thin materials and little gas pressure is required. 
The acetylene pressure should be one pound, the oxygen pres- 
sure two pounds. The No. 1 tip is suitable only for light gauge 
metals from 1/32 to 1/16 inch thick. The gas pressure should 
be the same as for the No. 0, or one poimd acetylene and two 
pounds oxygen. 

10 



The tips, as you already know, are readily interchangeable. 
To change tips is simply a matter of loosening the tip nut, re- 
moving the tip and replacing it with another and screwing the 
nut firmly to place. The operation takes but a few moments, 
and there is no excuse for not changing the tip and using the 
one best suited to the work. Even if you have only an inch 
of welding to do it is better to change the tip than to fuss along 
with a flame too large or too small. It is a bad habit to fall 
into, and should be avoided. 

You will note in the table that the No. 6 tip which is pro- 
vided for use with the large Style C torch should be used for 
metals from 5/16 to ^ inch thick, and that the acetylene pres- 
sure should be six pounds and the oxygen pressure twelve 
pounds. The acetylene pressure is the same as the number 
of the tip and the oxygen pressure is two times the number of 
the tip, or twelve pounds. This rule holds for all tips from No. 
to 6 inclusive but it does not hold true with the higher num- 
bers of tips. The No. 12 tip requires an acetylene pressure of 8 
pounds and oxygen pressure of 24 pounds. However, the rule 
of setting the acetylene pressure to the number of the tip, and 
making the oxygen pressure two times the number of the tip 
holds true throughout a large range of commercial welding. 

When using gases from acetylene and oxygen cylinders it 
is customary to break the rule to the extent of making the 
working pressures slightly more than the theoretical or table 
pressures when starting to weld. This is done to compensate 
for the loss of pressure as the gases are used from the cylinder. 
Regulators are likely to let the working pressure drop as the 
cylinder pressure falls ; hence it is customary when using gases 
from cylinders to set the regulators to one or two pounds 
above the table pressures. But when the gases are supplied 
through the pipe lines, as they are in the welding institute 
workroom, they are under nearly constant pressure, and you 
should set the regulators closely to the pressures specified in 
the tal)le. 

Care of Torch and Tips 

When changing the tips be careful to wipe the tip clean so 
that no dust or foreign substance will remain on the conical 

11 



ground seat and prevent it fitting closely in the head. If this 
precaution is not observed you are likely to have trouble from 
the gases leaking by the tip and causing flashbacks and other 
troubles. Always keep the tips standing vertical in a suitable 
box or holder, and keep them covered. This will insure the 
conical ground seats being protected from bruising and col- 
lecting dust. 

The needle valves seldom give trouble. If one should de- 
velop a leak it is doubtless due to dirt or scale getting on the 
seat and preventing the conical point seating properly. It can 
be readily removed and the foreign substance cleaned out. In 
general, however, avoid taking apart unnecessarily. Follow 
the very good rule of not tinkering with any apparatus when 
it does not require it. 

The oxy-acetylene torch is a simple and durable apparatus 
but it is not fool-proof. Always hang it up when through with 
it. Don't let it lie around on the bench as something may fall 
on it and spring it out of shape. Never use the head as a 
hammer. If you knock the work around with it you are likely 
to injure it and cause trouble. The head casting is bronze and 
though the bronze is of high tensile strength and great dur- 
ability it is easily dented by a blow. If dented the conical seat 
will be distorted and the tips will not fit ; consequently the 
gases will leak by the tip and cause trouble. The late model 
torches have drop-forged heads and these also should be 
handled carefully. 

When using the torch take good care of the end of the 
tip. If you let it drop occasionally into the puddle you are 
likely to cause a flashback or melt the end of the tip, distort 
its shape and perhaps clog the hole. A good workman is 
known by the way he cares for his tools, and the oxy-acetylene 
welding operator is no exception to the rule. Never attempt 
to remove the tubes in the head. They are sweated in with 
silver solder and can only be taken apart by an expert who is 
provided with the proper tools and apparatus. If your torch 
requires a new head, it should be sent to the factory where it 
will be inspected and the defective parts will be replaced. 

12 



Questions 

1. What is the form of the simple blowpipe used by- 
jewelers? 

2. What is a simple Bunsen burner? 

3. Where is the oxygen taken from to supply the flame 
of a simple Bunsen burner? 

4. What is the source of oxygen in a shop Bunsen torch 
using illuminating gas and compressed air? 

5. Who discovered the oxy-acetylene blowpipe? 

6. What is the blowpipe called in America? 

7. What is the mixing chamber like in principle? 

8. Where is the mixing chamber in the Davis-Bournon- 
ville torch? 

9. Is the interchangeable tip system advantageous? 
Why? 

10. What are the needle valves? The handle? The 
tubes? The head? 

11. How is the tip held in the head? 

12. What pressures of gases are required for welding 
^-inch steel? 

13. What size of tip should be used for welding ^-inch 
metal? 

14. How is the head secured to the tubes? 

15. What is the danger of letting a flashback burn in 
the tip? 

16. How close should the tip be held to the metal when 
welding? 



13 



Not 



es 



14 



Notes 



15 



Copyright 1919 by the 
Davis-Bournonvii,t.e Company 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



EXPLOSIVE GAS MIXTURES- 
FLASHBACKS AND BACKFIRES 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonvili,e Company 



EXPLOSIVE GAS MIXTURES-FLASH- 
BACKS AND BACKFIRES 

Combustion of Common Fuel Progressive — Combustion of Air and Combustible 
Gas Mixture Sudden and Explosive — Coal Mine Explosions Due to Mixture of 
Mine Gas and Air — Flame Propagation — Principle of Davy Mine Safety Lamp — 
Application in Oxy-Acetylene Torch — Flashbacks and Backfires — Importance of 
Correct Procedure in Starting to Weld — How to Set up the Apparatus and Blow^ 
Out Foreign Substances — What to Do in Case of Stoppage. 

When a candle is lighted the wick takes fire and the wax 
beneath melts and forms a pool of liquid which saturates the 
wick and feeds the flame. As the candle burns it becomes 
shorter and shorter. The burning or combustion of the wax 
or wick is progressive and practically constant. So it is with 
ordinary fire. If we start a fire of sticks and shavings the 
fuel is progressively consumed. The rate of combustion may 
not be constant, however, as that will depend on how the 
fire is built and whether it is in a firebox or open grate, 
but the fuel does not burn all at once. It burns until the 
wood is gone, and then it goes out. When you light a gas- 
jet, the rate of combustion is constant. The gas burns as 
it escapes from the jet; the flame remains practically the 
same size, and the consumption of gas is a certain number 
of cubic feet per hour. 

Combustion of Air and Combustible Gas Mixture 
Sudden and Explosive 

But if we let some gas escape unburned into a bottle 
and then apply a match to the opening we get instantaneous 
combustion and an explosion. The gas mixes with the air 
when it enters the bottle and forms a mixture that burns 
instantly. When the match was applied to the mouth of the 
bottle the flame spread instantly in all directions, and the 
gas and air combined in a fraction of an instant. The re- 
sult was a tremendous expansion of the air and gas due to 
the heat produced, and a loud noise or report. 



Explosive mixtures of gas and air are always danger- 
ous and should be avoided. Never look for a gas leak in the 
cellar with a lighted candle ; you are likely to be a subject 
for the coroner if you do. The gas escaping into the cellar 
mingles with the air and forms an explosive mixture which 
may be of sufficient volume and power to blow the house 
from its foundation and kill the occupants. 

Coal Mine Explosions Due to Mixtures of Mine 
Gas and Air 

Coal mine explosions occur in coal mines in which ac- 
cumulations of combustible gases are released by removal of 
the coal. The explosion is caused by the accidental ignition 
of the mixture of this coal gas and the air which has reached 
the explosive state. It is a curious fact that a mixture of 
combustible mine gas and air is not explosive when the pro- 
portion of gas to air is much greater than a certain figure 



SOLID FUEL 

WOOD OR COAL,TO GAS 

SLOW COMBUSTION 



|1 jll ,ll />.■' All 



SOLID FUEL 

TALLOW OR PARAFFINS, TO GAS 

SLOW COMBUSTION 



AIR AND GAS MIXED 
INSTANTANEOUS EXPLOSION 




Davis Bournonville Institute 



FIG. 1. OPEN FIRE, CANDLE FLAME, GAS JET AND INSTANTANEOUS 

COMBUSTION COMPARED. 

generally about 10 to 12 per cent; neither will a mixture of 
mine gas and air explode if less than a certain figure, say 
about 8 to 9 per cent. While the over-rich mixture is non- 
explosive up to a certain figure it again becomes explosive 
when very rich. Thus, we have the condition first of the 
non-dangerous mixture of gas and air up to about 8 or 9 per 



cent dilution depending on the quality of the gas ; from 8 
to 12 per cent is a highly dangerous mixture ; and from 12 
per cent to about 80 per cent or 85 per cent may not be 
violently explosive but slightly greater dilution may again 
create an explosive condition. Acetylene gas, however, forms 
an explosive mixture with air when the mixture reaches 3 
per cent acetylene. All gas mixtures in closed places are 
potentially dangerous and should be treated very cautiously. 
The odor of acetylene is noticeable when a very small per- 
centage is present, and the warning should never be disre- 
garded in closed places. 

Flame Propagation — Principle of Davy Safety Lamp 

Extensive experiments conducted by the Bureau of Mines 
to determine the explosibility of gas mixtures have not only 
determined the percentage of gas mixture that is dangerous 
but they have also determined the rate of flame propagation 
in an explosive mixture. Many hard coal mines would be un- 
workable were it not for the Davy safety lamp. The safety 
principle of this lamp was discovered by Humphrey Davy 
many years ago and it has proved to be one of the most 
valuable safety devices. The safety feature of the Davy lamp 
is very interesting as it has an important bearing on the 
action of the oxy-acetylene torch. Humphrey Davy discov- 
ered that an open flame in the miner's lantern could be made 
safe by surrounding it with a fine mesh metal gauze — in other 
words, woven wire cloth. The gas and air entering the lan- 
tern through the gauze burns quietly and without explosive 
effect. Remove the wire gauze envelope and immediately the 
surrounding gas laden air takes fire and explodes. 

The reason for this apparently strange action is easy to 
understand when explained. Flame is incandescent gas ; it is 
gas in the state of combustion. If the flame is cooled it dis- 
appears and no longer ignites an adjacent combustible mix- 
ture. The metal gauze cools the flame spreading from the 
light and prevents its propagation. 

We have here two candles. One is lighted and the other 
is not. When we touch the flame of the lighted candle to 





ACETYLENE 







FIG. 2. SHOWING THREE CONDITIONS OF FLASHBACK, TWO OF 

WHICH HAVE DEVELOPED BACKFIRE. 

the wick of the unlighted one it immediately takes fire and 
burns. Now we will blow one candle out and bring the 
flame of the other close to the wick but not touching it. 
It immediately takes fire. Why? The gas escaping from 
the hot wick is combustible and the adjacent flame starts 
combustion. 

Now we will blow the candle out again and bring the 
lighted one close to the wick as before but with this fine 
wire gauze between. The unlighted wick no longer catches 
fire when the flame is brought close to it. In fact, it will 



not take fire when the gauze is placed directly against the 
wick, and the lighted candle is brought close up to the gauze. 
Why is this? 

The reason is that the gauze being metal and compara- 
tively cool reduces the temperature of the flame below the 
igniting point. The metal radiates the heat rapidly and we 
could hold the flame close to the wick with the gauze be- 
tween for a long time before the metal would get hot enough 
to fire the unlighted wick. 

This, then, is the principle of the Davy safety lamp. The 
explosive air and gas passes through the gauze to the flame 
and burns but the flame cannot propagate through the gauze 
because the moment it reaches the gauze it cools below the 
igniting point. The gauze, in fact, is a refrigerator or icy 
barrier that stops the flame and thus preserves the miner 
from the dangers of a mine explosion. 




BURNT METAL 



PASSAGE OBSTRUCTED 



FLASH BACK 

FLAME PROPAGATION 

GREATER THAN VELOCITY 

OF ESCAPING GAS 



Davis Bournonville Institute 



FIGS. 3 AND 4. — SHOWING NORMAL FLAME AND FLASHBACK FROM 

EXTERIOR. 



Application in Oxy-Acetylene Torch 

You have the Davy principle in effect in the tip con- 
struction of the oxy-acetylene torch. The holes through which 
the combustible gases enter the mixing chamber are of small 
diameter and comparable in dimension to the mesh of the 
wire gauze in the safety lantern. If the flame tends to fol- 
low the mixture of oxygen and acetylene back into the tip 
and into the head the tendency is checked ordinarily by 
the rapid flow of the gases and the cooling effect of the tip. 
Under normal working conditions the head and tip are com- 
paratively cool and the flame entering the tip is extinguished. 
Moreover, the velocity of the escaping gases is high, and 
in excess of the flame propagation rate. Should, however, the 
tip become very hot and the flow of gases be momentarily 
checked, then it is possible for the flame to enter the tip 
and pass back into the mixing chamber and burn there. This 
is called a flashback. If a flashback penetrates beyond the 
mixing chamber into the torch handle, hose, or even to the 
regulator chamber, it is called a backfire. 

Flashbacks and Backfires 

The terms flashback and backfire are loosely interchanged 
but there is a well defined difference which should be clearly 
understood by all using the oxy-acetylene apparatus. The 
first is a more or less petty annoyance due to local con- 
ditions, while the other is serious and demands an investiga- 
tion to determine the cause. To make the distinction clear 
we will again state the action of each and the causes that 
produce them. 

A flashback is the snapping out of the flame and pene- 
tration of the flatne into the torch tip or mixing chamber. 
It is generally caused by an obstruction in the tip such as 
a globule of metal adhering to the end or by holding the 
tip too close to the puddle and thus obstructing the flow 
of gas so that the flame is able to propagate back to the 
mixing chamber. A flashback is checked by shutting off the 
oxygen needle valve. The fire in the torch is immediately 
extinguished and the pure acetylene gas issuing from the 
tip may be relighted and then the oxygen needle valve opened 



and adjusted as before. Overheating of the tip due to use 
on a preheated casting or long continued welding in a closed 
place may cause popping back. Cooling of the tip may then 
be necessary but ordinarily the Davis-Bournonville torch 
never requires dipping into a pail of water to keep it cool. 

A backfire is a much more serious matter than a flashback 
as it may burn or burst a hose and scare the operator. In a 
manufacturing welding room where operators are close to- 
gether a bursting hose might cause a panic and result in 
the injury of some of the welders, especially if girls. A back- 
fire results in the penetration of the flame through the torch 
into the handle, hose or pressure regulator and is caused by 
an accumulation of mixed gases due generally to faulty manip- 
ulation of the cylinder stop valves, improper regulator ad- 
justment, incorrect procedure of turning on and lighting gases 
or dipping the tip into the puddle. It is of the utmost im- 
portance that welding operators be required to follow a fixed 
procedure in turning on and lighting the torch both for their 
own safety and the safety of others. Even though a backfire 
may cause no more damage than the bursting of a hose, that 
is serious enough. A burst hose means the destruction of 
property and time lost in replacing it. It is a reflection on 
the operator's ability and may cause the uninformed observer 
to conclude that there is something radically wrong with the 
whole apparatus. 

We have given considerable attention to the principle 
of the Davy safety lamp. Do not get the idea that the metal 
gauze strainers in the gas regulators are effectual barriers to 
flame propagation, however, because unfortunately they are 
not. The heat of the oxy-acetylene backfire is so intense 
that the cooling effect of the gauze is overcome, the gauze 
melted and the flame passed on beyond. This will give you 
an idea of the intensity of the heat at your command. The 
gauze strainers may tend to check the flame but they can- 
not be depended on with certainty. The function for which 
they are designed is to stop scale and dirt from: entering the 
torch and clogging the tip. 

The illustration. Fig. 2, shows in diagram four conditions 
of combustion that may develop in the oxy-acetlylene torch 



apparatus. The normal condition is shown at A for a weld- 
ing torch in which acetylene is supplied under five pounds 
pressure and oxygen under ten pounds pressure. The pro- 
portions of the mixing head or carburetor and the outlet 
are such as to give a stable flame. But at B the balance 
has been lost due to overheating of the torch head, obstruc- 
tion in the tip or an excessively oxidizing flame. The flame 
has popped back or propagated to the mixing chamber where 
it continues to burn. This is a flashback. A more serious 
condition is shown at C which may develop as a consequence 
of holding the tip immersed in the puddle causing a flash- 
back and prolonging the abnormal state. The outlet is 
stopped and the oxygen pressure being in excess of the acety- 
lene pressure tends to equalize which results in the oxygen 
flowing back into the acetylene tube and burning there. This 
is the propagation of the flashback into the hose and is known 
as a backfire. 

A condition similar to C is shown at D but the oxygen 
pressure being less than the acetylene pressure the flashback 
is propagated into the oxygen hose. This is a serious hazard 
as it invariably ends in burning the oxygen hose and spat- 
tering burning molten rubber over the surroundings. It is 
an inherent hazard of the equal pressure or balanced pressure 
torch. 

The three conditions shown are the result of a flash- 
back and its propagation. A backfire is regarded as a propaga- 
tion of a flashback into mixed gases, and may take place in 
the torch handle, hose, regulator or even as far back as the 
acetylene generator if proper safeguards are not provided in 
the acetylene gas line. 

Importance of Correct Procedure 

In the lecture "Regulating Gas Supply" detailed instruc- 
tions were given for opening the valves and gas regulators. 
You were told to open the cylinder valve on the oxygen 
cylinder first, and to open it very slowly but to open it full. 
The reason for opening it slowly is that a sudden rush of 
oxygen gas at a pressure of 1,800 or 2,000 pounds per square 
inch may injure the diaphragm in the gas regulator and make 

10 



it unworkable. The reason given for opening the valve as 
far as it will go is to prevent leakage around the stem. The 
cylinder valve is made with two seats, one of which acts in 
the ordinary manner to check the flow of gas while the other 
backs up against another seat beneath the stufhng-box end 
and prevents the leakage around the stem when the valve 
is open. 

You were directed to open the oxygen valve first and 
to regulate the oxygen regulator while the oxygen needle 
valve is open. The reason for having the needle valve open 
is that you will be unable to adjust the working pressure 
accurately if the gas is not escaping the same as when being 
used. The reason for opening the oxygen valve first and 
regulating the flow is to prevent forming a mixture with the 
combustible in the torch tubes or hose. Oxygen is not com- 
bustible ; it supports combustion only. You cannot light the 
oxygen gas when it is escaping from the tip alone, but you 
can light the acetylene when it is escaping from the tip alone 
— because the flame takes the necessary oxygen from the air. 

Now consider what might happen if the acetylene gas 
valve was opened first and the acetylene regulator was ad- 
justed first. The torch would be filled with acetylene gas, 
and when the oxygen was admitted the operator might not 
let it flow long enough to clear out all the acetylene and 
oxygen mixture. The result may be a disagreeable backfire 
when the gas is lighted. Even if no damage results the 
effect on the nerves is something to be avoided. 

Causes of Trouble Reviewed 

To reiterate, there is little danger of flashbacks and back- 
fires if the operator knows his business and attends to it. 
He needs only to follow the rules in opening the valves, 
regulating the gas supply and manipulating the torch to avoid 
them. Under normal conditions the flame cannot enter the 
torch or hose. The velocity with which the gases escape is 
greater than the speed of the flame traveling in an explosive 
mixture. The gas coming out pushes the flame ahead of it 
and keeps it at the tip where it belongs. Experiments have 

11 



shown just how quickly a flame spreads in an explosive 
gas mixture. This rate or speed called the "speed of flame 
propagation" is from 300 to 600 feet per second, depending 
on conditions, the gases, etc. We can burn an explosive 
mixture of acetylene and oxygen at the tip if the speed 
of the gases escaping is greater than the rate of flame propa- 
gation. If the speed of the gases escaping is greater than 
the rate of flame propagation, the flame cannot enter the tip 
and follow back into the hose ; the gases are coming out 
faster than the flame can travel against them. Keep this 
fact in mind and avoid doing anything that removes this 
safeguard. 

When the valves are properly adjusted a flashback or 
backfire can occur only when something checks the flow of 
gas or the head and tip become overheated. If you hold 
the tip too close to the metal you may check the flow of 
gas so that the flame can enter the tip. This will cause the 
flame to pop out sometimes, but very rarely will it follow 
back into the hose. 

How to Set Up Apparatus and Blow Out 
Foreign Substances 

If care is not taken to blow out the hose before connect- 
ing up, loose dirt may enter the torch and clog the tip so 
that the gas cannot flow freely. The operator should follow 
a certain set procedure when setting up welding or cutting 
apparatus as follows : 

1. Before attaching the oxygen regulator to the cylin- 
der "crack the valve" to blow out any dirt that may 
have lodged in the opening. 

2. Clean off any dirt that may have lodged on the 
nipple connection of the regulator, and shake it with 
the opening down so that any loose dirt within will 
rattle out. 

3. Connect the regulator to the gas cylinder and crack 
the cylinder stop valve slightly and blow gas through 
the regulator for a moment. 

4. Connect the hose to the regulator and again blow 
through. 

5. Connect the hose to the torch, open the needle valve 
and again blow through. 

12 



6. Repeat the procedure with the acetylene regulator 
and hose connection. 

If in the course of welding or cutting the torch begins 
to give trouble and the cause is suspected to be some foreign 
substance, proceed as follows to remove it : 

Disconnect the hose from the torch and blow each hose 
out separately. Remove the torch tip and open the needle 
valves, and insert the nipple of the oxygen hose into the 
head and blow through. This should remove any ordinary 
obstruction. 

Above all, avoid getting excited when things don't work 
properly. Remember always that fixed laws govern the work- 
ings of the oxy-acetylene apparatus the same as of every- 
thing else. If it refuses to work satisfactorily there is a 
cause, and it is up to you to find it and remedy the trouble. 

Questions 

1. What sort of combustion takes place in a coal fire? 

2. Why does a mixture of air and gas explode? 

3. What is an explosion? 

4. What is the rate of flame propagation in a coal mine 
explosion? 

5. Why does the Davy safety mesh prevent firing ex- 
plosive mixtures in mines? 

6. Is the Davy screen effective in oxy-acetylene ap- 
paratus? Why? 

7. Does the cooling principle apply at all in the torch? 

8. What is a flashback? 

9. In what respect does a flashback differ from a back- 
fire? 

10. What should be done immediately when the flame 
pops back? 

11. How many conditions of flashback and backfire are 
recognized? 

12. Is a certain set procedure important in starting to 
weld? 

13. What should be done first in setting up the equip- 
ment? 

14. How do you blow out the torch if it becomes stopped ? 

15. What advice should be observed when things go 
wrong? 

13 



Notes 



14 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

HEAT AND TEMPERATURE 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 




y//.-v/.\y. ■? 



TEMPERATURE-2800'^ F 

LARGE VOLUME OF HEAT 




Vu.^^% 




MIXING CHAMEER_J ^ 




Davis Bournonville Institute 



HEAT AND TEMPERATURE OF OXY-ACETYLENE TORCH AND BOILER 
FURNACE COMPARED 



HEAT AND TEMPERATURE 

Heat and Temperature Not the Same — Radiation, Convection and Conduc- 
tion — British Thermal Unit Measure of Heat — ^Temperature Measured with 
Thermometers or Pyrometers — Expansive Effect of Heat — Specific Heat — Oxy- 
Acetylene Torch Means of Producmg High Temperatures. 

You probably think of heat and temperature as one and the 
same thing, but they are not the same ; it is highly important that 
you clearly understand the difference and are able to make the 
distinction. You will understand the oxy-acetylene torch action 
much more clearly when you realize the difference between a large 
fire and a very hot fire. 

A Large Fire may be no Hotter than a Small One 
— Radiation — Convection and Conduction 

A large fire is not necessarily a very hot fire. A large fire 
fire gives off a great amount of heat, but the temperature may 
never rise much above 2000 degrees Fahrenheit. When an open 
fire, burning any combustible like wood, rises to a certain tem- 
perature it can become no hotter, no matter how long it burns 
or how much fuel is added. There is a limit to the intensity of 
combustion, but the limit to the amount of heat produced is the 
amount of fuel consumed. If heat must be provided for a small 
room, a small coal stove or a gas-heater will be sufficient, but if a 
whole house is to be heated a large furnace must be used. The 
temperature of the furnace fire will be little higher, if any, than 
the temperature of the small coal fire, but the furnace will give off 
a much greater volume of heat, and it wih warm more rooms 
than the small coal stove, because more coal can be burned in the 
furnace than in the small stove. 

Heat is dissipated by radiation, convection and conduction. 
Heat rays are invisible. A fireplace warms a room by radiated 
heat chiefly, the rays from the fire give the body the sensation 
of warmth and comfort on the side facing the fire, even when the 
air in the room is comparatively cold. A steam radiator heats 
the air and radiates invisible heat rays also. The fireplace fire 



is inefificient because most of the heat goes up the chimney with 
the smoke and gases of combustion. The steam radiator heats 
chiefly by convection ; the air circulating over it finally fills the 
room and all parts become warm. Heat travels by conduction 
in a metal piece. If one part is made very hot the heat flows to 
the colder parts and warms them. When you hold the red hot 
end of a steel bar near your face you feel radiated heat. If you 
hold your hand over the bar you will feel hot air rising from it; 
that is heat of convection, and if you hold the bar long enough 
it will become unpleasantly hot at the lower end. That is due 
to conducted heat. Remember that heat tends always to equalize 
the temperature by traveling from hot zones to cooler ones. 

Heat Can Be Measured 

The practical man is likely to look upon science as being some- 
thing impractical and beyond his comprehension. But that is a 
very erroneous view. While some scientists are impractical in 
workaday matters they have, as a class, found out the methods 
of weighing and measuring imponderable substances and unseen 
forces, and thus making them available for practical purposes. 
Now when you can measure something or weigh it you ca i deal 
with it understandingly. It no longer is mysterious. Electricity 
was a very mysterious and incomprehensible force until the 
scientists learned how to produce it, to measure its capacity, to 
weigh its force and to control and direct it. Then the practical 
man could apply it to useful purposes. 

Heat can be measured and the amount of heat in a pound 
of coal may be accurately determined. Heat is measured by 
thermal units, or in calories in the French system used by scien- 
tists. A British thermal unit is the amount of heat required to 
raise the temperature of 1 pound of water 1 degree Fahrenheit. If 
one pound of water is raised in temperature 100 degrees it has 
absorbed 100 British thermal units. (Abbreviated to B. T. U.) 
A pound of clean coal when so burned as to secure perfect com- 
bustion generates about 13,000 B. T. U., a pound of kerosene 
about 20,000 B. T. U., and a pound of acetylene about 23,000 
B. T. U. Authorities differ on these figures, especially on acety- 
lene. 



Thermometers Used To Measure Temperatures 

The intensity of the source of heat is the temperature. Tem- 
peratures are measured with thermometers or pyrometers. A 
glass thermometer may be used when the temperature is 
comparatively low, say up to 400 or 500 degrees Fahrenheit. 
High temperatures, such as are encountered in a furnace, are 
measured with pyrometers. The common form of a pyrometer 
comprises two dissimiliar metal wires which are twisted together 
at one end, and separated by some insulating material like porce- 
lain that withstands a high heat. The twisted ends of the wires 
are thrust into the furnace. The other ends are connected to a 
millivolt meter which records the feeble electric current produced 
by the metal couple when highly heated. The graduations on the 
the dial of the millivolt meter indicate the temperature in degrees. 

Another form of pyrometer works on the optical principle. 
The light emitted by the furnace is compared with the filament 
of an incandescent electric lamp, and by this comparison the 
observer is able to tell the temperature of the furnace. 

The temperature of this room is measured by a glass ther- 
mometer. It registers about 68 degrees Fahrenheit. This is a 
Fahrenheit thermometer because it has the Fahrenheit scale. The 
two standards of measuring points of the Fahrenheit scale are 
the melting point of a mixture of finely chopped ice and salt, and 
the boiling point of pure water at sea level. The melting point 
of ice and salt is called zero. The space on the tube between the 
zero point and the boiling point is divided into 212 graduations 
called degrees. Pure water freezes at 32 degrees on the Fahren- 
heit scale. Therefore there are 180 degrees between the freezing 
and boiling points. 

Thermometer Scales 

The Fahrenheit scale is commonly used in shops and factories 
and is the common scale of every-day use to indicate the tem- 
perature outdoors and indoors. There is another thermometer 
scale commonly used in scientific work called the Centigrade 
scale. In the Centigrade scale the zero point is the freezing point 
of pure water at sea level and the boiling point is the other ex- 



treme of the scale. The space between the freezing and boiling 
point is divided into 100 parts, each of which is called a degree. 
There is still another thermometer scale — the Reaumur — but little 
used and seldom referred to in text books. The zero point is the 
temperature of freezing pure water and the space between this and 
the boiling point is divided into 80 parts or degrees. 

In the Fahrenheit scale there are 180 degrees between the 
freezing point and the boiling point of pure water at sea level, 
while in the Centigrade scale there are only 100 parts. Hence, 
it is apparent that the Fahrenheit and Centigrade degrees are not 
the same ; 1 degree Centigrade is equal to 1.8 degree Fahrenheit. 
The Centigrade scale is generally used, as we have said, for scien- 
tific work and the Fahrenheit scale is used for common purposes. 
When temperatures are mentioned hereafter in these lectures 
they will be in the Fahrenheit scale. The abbreviation for 
Fahrenheit is F. and for Centigrade C. 

From the foregoing it should be clear that temperature may 
be compared to pressure while heat may be compared to volume 
or quantity. We may use the water pipe analogy. If a water pipe 
carries water under pressure, the pressure can be determined by 
the use of a pressure gauge. The temperature of the water 
wOuld be determined by a temperature gauge or thermometer. 
The amount of water flowing through the pipe could be measured 
by a meter. We have no simple meters for heat but you can 
imagine that the amount of heat could be measured by something 
like a meter. We are, in fact, able to determine the amount of 
heat in a given volume of water, very readily from the tem- 
perature, the weight of the water and its specific heat. 

Specific Heat 

Specific heat is the quantity of heat required to raise the tem- 
perature of a body 1 degree in comparison with water; water is 
the standard. The specific heat or heat capacity of metals is less 
than that of water. The specific heat capacity of some metals 
is much greater than others. This has an important effect on 
welding with the oxy-acetylene torch. A metal that has high 
specific heat, or heat capacity is more difficult to weld than one 



that has low specific heat. This is a characteristic quite different 
from the melting point. The melting point may be comparatively 
low while the specific heat is high as is the case of aluminum. 

What has been said should make it clear that heat and tem- 
perature are not the same, but they are closely related. There can 
be no heat without temperature, and no temperature without heat. 
The higher the temperature the more rapidly will the heat flow 
to bodies of lower temperature. The higher the temperature of 
your torch flame the more quickly will it melt the steel or cast 
iron. The temperature of the hottest part of the oxy-acetylene 
flame is about 6300 degrees F. It is so high that almost all solid 
substances melt and run like water when exposed to it. The tem- 
perature is the highest known with the exception of the electric 
arc. The temperature of the electric arc is supposed to be about 
7800 degrees F. 

Expansion and Contraction 

Changes of temperature affect the length, breadth and thick- 
ness of a metal piece. If the temperature is raised the part ex- 
pands and if the heat is abstracted and the part cools it shrinks. 
The changes are proportional to the changes of temperature 
within a wide range of limits. If you know that a steel bar two 
feet long is to be heated up 1000 degrees F. you can calculate 
very closely the amount of expansion, and make allowance for 
it. The change in length due to change of temperature is called 
the coefficient of expansion or contraction, and it has been de- 
termined for all the metals. The coefficient is a factor generally 
expressed as a fraction of inch and for 1 degree. A cast aluminum 
bar expands over 5/33 inch to the foot when heated from 60 
degrees F. to the melting point, or 1218 degrees. 

Amount of Heat Produced by Torch is Small 

Notwithstanding the fact that the hottest part of the oxy- 
acetylene torch flame has a temperature of over 6000 degrees F. 
the ajiwunt of heat given off by a torch flame is comparatively 
small. We can get much more heat from the blacksmith's forge 
because we burn much morel' fuel, and produce more thermal 



units in a given time, but we cannot get the high temperature. 
The temperature of the hottest forge fire is only about 2800 to 
3000 degrees F. 

When large masses of iron require heating to moderate tem- 
peratures, the economical method is to use a coal fire or an oil 
flame. The cost of the heat will be much less than when pro- 
duced with oxygen and acetylene. But when the metal must be 
melted and welded the high temperature flame is required. 

Now you begin to realize that you have in the oxy-acetylene 
torch a tool or instrument of extraordinary quality. Its flame 
is one of great intensity but remember that the zone of great in- 
tensity of temperature is confined to the white hot cone. The 
flame adjacent is comparatively cold. The cone tip is keen like a 
razor blade while the remainder is "dull as a hoe." 

When manipulating the torch then it is plain that the tip of 
the cone — the keen razor blade — should be applied to the parts 
you want to melt. Don't "hoe around" with the other part of the 
flame if you want to make progress. 



Questions 



1. Are heat and temperature the same? 

2. What do you understand by radiation, convection and 
conduction? 

3. What are the measures of heat? 

4. What is a British Thermal Unit? 

5. What are the means used to measure temperatures? 

6. What is the common thermometer scale? 

7. What is the boiling point of water on the Fahrenheit 
scale ? 

8. What is the effect of heat on a bar of steel? 

9. What temperature is produced by the oxy-acetylene 
torch flame? 

10. Is the amount of heat given off by the torch flame large 
compared with that produced by the blacksmith's forge? 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDIING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



OXYGEN 
AND ITS MANUFACTURE 



DAVIS -BOURNOINVILLE INSTITUTE 

JERSET CITY. N. J. 



Copyright 1919 by thb 
Davis-Bournoxvii,i,e Company 



OXYGEN AND ITS MANUFACTURE 

Oxygen a Common Element — Methods of Producing Oxygen — Liquid Air 
Process — Oxygen Cylinders, Tanks or Bottles — Weight of Oxygen and Oxygen 
Cylinders — Electrolytic Process of Producing Oxygen and Hydrogen — Pure Water 
Required for the Electrolyte. 

From the lectures on "Combustion" and "Flame and its 
Structure" we learned something about oxygen and the im- 
portant part it plays in the subject of combustion in general. 
The oxygen in the atmosphere is the supporter of life and fire. 
Because of its dilution the oxygen in the atmosphere cannot be 
made to develop the high temperature possible from the use 
of pure oxygen. Hence, methods of separating or producing 
oxygen in the commercially pure state have been very im- 
portant to the art of oxy-acetylene welding. In this lecture 
we propose to briefly describe how oxygen is manufactured 
and compressed into steel bottles for distribution and use. 

While it is not absolutely essential to your success as 
torch welders that you know all about the sources of supplies 
used in your work it is nevertheless highly desirable that any 
intelligent workman know something about the commercial 
side of his occupation. Most men have the ambition to be 
independent and run a business of their own. We hope that 
in the not distant future some of you at least will be running 
welding shops. You will then have to deal with the commer- 
cial side of the business, and the question of gases and other 
supplies will loom up large and important. i 

Oxygen a Common Element 

Oxygen is one of the most common elements in this world 
of ours. The air we breathe is made up of oxygen and 
nitrogen mixed in the proportion of about 23 parts of oxygen 
and 71 parts nitrogen. The oceans which cover three-fourths 
of the earth's surface are one-third oxygen by measure and 
the same applies to the fresh water of lakes, rivers and streams. 
The earth's crust is largely made up of oxides of one form or 



another but common as oxygen is it is never found in the 
pure undiluted state. It is either chemically combined or 
mixed with nitrogen in the atmosphere. It is not strange, 
however, that oxygen is never found in the free, pure state ; 
it has such a strong affinity or attraction for carbon, hydro- 
gen, metals and many of the earths that long ago in the early 
geological ages it formed combinations or close partnerships 
that can be dissolved only with difficulty. The important 
exception to the chemically combined state is the free oxygen 
in the air but it is much diluted, and although the atmosphere 
contains 23 parts oxygen in mixture with nitrogen and other 
gases it is not by any means an easy matter to separate them. 
It is only within comparatively recent years that processes 
have been developed by which the separation can be effected 
on a commercial basis. 

Commercial methods of producing pure oxygen have had 
a most important influence on the development of oxy-acety- 
lene welding and cutting. In fact, the processes could never 
have reached the important stage of development they now 
have attained had it not been for the enterprise of the concerns 
that developed oxygen production methods and plants for com- 
mercial distribution. The discovery of a commercial method 
of producing calcium carbide and cheap acetylene was only 
one step in the development. Cheap oxygen commercially 
distributed was also required in order to put the industry on 
a sound basis. 

Methods of Producing Oxygen 

There are. three general methods by which oxygen may 
be manufactured. They are, in order of importance, as fol- 
lows : the liquid air process, the electrolysis of water process 
and various chemical processes. Chemical separation methods 
were first employed for the commercial production of oxygen 
used in the oxy-acetylene process. It is comparatively easy 
to drive off oxygen from chlorate-of-potash, for example, it 
being necessary only to heat the chlorate in a closed retort 
and collect the oxygen, as it escapes. Manganese dioxide is 
mixed with the chlorate-of-potash but apparently takes no 



part in the chemical reaction. Its effect is to reduce con- 
siderably the temperature at which the chlorate gives up its 
oxygen. Thus, the use of manganese dioxide saves fuel and 
reduces the cost of furnace upkeep. 

There are other chemical processes of making oxygen, 
among which may be mentioned the chloride-of-lime process, 
the sodium peroxide process, the barium monoxide or Brin's 
process. None of the chemical processes are now considered 
commercial in this country except perhaps, for certain remote 
localities where it may be easier to get chemicals than bottled 
oxygen. The cost of the chemicals and the necessary labor 
are so high that the oxygen produced by chemical processes 
is, in general, much higher than that made by the liquid air 
or electrolytic processes. 

Liquid Air Process 

A volume could be written on the liquefaction of gases, 
the discovery of liquid air and the subsequent development 
of the fractional distillation process by Prof. Linde in 1897. 
The liquid air process is based on the fact that air can be 
liquefied by the process of compression, expansion and conse- 
quent refrigeration. High hopes were entertained of the 
commercial value of liquid air but they have not been realized 
except in the production of gases. When the air is liquefied 
and allowed to evaporate, the nitrogen evaporates first at a 
temperature of about 20 degrees F. higher than the boiling 
point of oxygen. Hence, if care is taken it is possible to boil 
out the nitrogen and leave the liquid oxygen. The oxygen 
thus produced is commercially pure, containing but little 
nitrogen and other gases and some impurities that are in the 
atmosphere. 

The commercially pure oxygen is pumped into seamless 
steel bottles or cylinders for distribution and use. These steel 
bottles are drawn with hydraulic presses from steel billets, 
and though the shell is thin and light the cylinder, neverthe- 
less, is very strong. Each cylinder is subjected to a hydraulic 
test pressure of about 3600 pounds per square inch to discover 
leaks and defects. The cylinder stop valves arc provided with 



safety discs designed to blow under excessive pressure or 
temperature. The oxygen is pumped into the cylinders to a 
maximum pressure of 1800 to 2000 pounds per square inch. 
Formerly the maximum was 1800 pounds but during the 
war period the manufacturers raised the pressures to 2000 
pounds in order to conserve cylinders, steel and transportation 
facilities. A cylinder filled with oxygen to a pressure of 2000 
pounds contains one-ninth more oxygen than if compressed 
to a pressure of only 1800 pounds. In other words, a 200- 
cubic foot cylinder holds 220 cubic feet when the oxygen is 
compressed to 2000 pounds. 

Oxygen Cylinders, Tanks, Flasks or Bottles 




Davis Bournonvllle Institute 



Fig. 1. PORTABLE OXY- ACETYLENE WELDING OUTFIT SHOWING 
TYPICAL OXYGEN AND ACETYLENE CYLINDERS 

6 



The commercial pressure containers for the gases used for 
welding and cutting are called cylinders, tanks, flasks or bottles. 
But the term cylinder seems to be preferable to tank or bottle. 
The term bottle is more appropriate to the seamless cylinders 
used for laboratory work and for physicians. The work tank 
ordinarily means a stationary container used under little or 
no pressure except that due to the weight of the fluid con- 
tained, and often it is open at the top. The term flask is seldom 
used to designate a gas cylinder. 

Weight of Oxygen and Oxygen Cylinders 

The weight of 100 cubic feet of dry oxygen is about 8.9 
pounds and one cubic foot weighs 1.42 ounce. A 200-cubic 
foot oxygen cylinder weighs about 142 pounds when filled and 
124 pounds empty, the average weight of the full and empty 
cylinder added together and divided by 2 being 133 pounds. 




Oa"is Bournonville Institute 



Fig. 2. oxygen pressure regulator with low pressure and 
high pressure gauges, the high pressure gauge being 

graduated to INDICATE CUBIC CONTENTS AS 
WELL AS PRESSURE 



The contained oxygen in a charged cylinder weighs close to 
18 pounds. 

It is not necessary, however, to resort to the weight 
method to ascertain the amount of oxygen remaining in a 
cylinder, inasmuch as the amount remaining is very nearly 
porportionate to the drop in pressure, if the temperature 
remains constant. If the cylinder pressure is 1800 pounds per 
square inch at the start, the drop in pressure per cubic foot 
withdrawn will be 1800 divided by the cubic foot capacity in 
feet or 200, if it is a 200-cubic foot cylinder. Hence, the drop 
is 9 pounds per cubic foot withdrawn. If 120 cubic feet have 
been withdrawn the drop should be approximately 1080 pounds 
and the gauge should indicate but 720 pounds pressure. 

Air reduction methods of producing oxygen have de- 
veloped commercially to a great importance and are, as stated, 
the chief means of producing commercial oxygen. But these 
processes have the disadvantage of requiring a costly plant 
that must be operated by experts and it is not feasible nor 
allowable for a manufacturer to produce his own oxygen 
from the atmosphere. The bottled oxygen must be shipped 
from central distribution plants, and the empty cylinders have 
to be returned at considerable expense and trouble. These 
disadvantages give to the electrolytic processes commercial 
advantages under some conditions, and we will describe the 
process and apparatus in some detail. 

Electrolytic Process of Producing Oxygen 
and Hydrogen 

The electrolytic process of producing oxygen and hydro- 
gen from water is a fascinating study in the principles of 
chemistry and electricity. It is one of common chemical 
experiments performed in the laboratory to demonstrate the 
composition of water and it never fails to excite interest and 
wonder. It is hard for the practical man to believe that the 
water we drink, all the water in seas, lakes, rivers and streams 
and that snow and ice are composed of two invisible gases, 
but it is true. All water is made up of oxygen and hydrogen 
chemically combined in the proportion of one part oxygen to 



two parts hydrogen. The familiar chemical formula for water 
is HoO which means that the water molecule is composed' of 
two atoms of hydrogen and one atom of oxygen. 




Davis Bournonville Institute 



Fig. 3. davis-bournonviille electrolytic generator for 
producing oxygen and hydrogen from water 



When water is separated into two component gases by 
passing a current of electricity through it the hydrogen collects 
on the negative electrode and the oxygen on the positive 
electrode. It is then merely a matter of cell construction to 
keep the gases separated and to provide means for drawing 
of¥ the two gases into separate containers where they are 
immediately ready for distribution and use. But, of course, 
there is much more to the apparatus for separating oxygen 
and hydrogen from water than in the simple experimental 
apparatus used in the laboratory for demonstration purposes. 
Although apparently simple, the fact is that the development 



CROSS SECTION OF 
THREE WAY VALVE 



-UPPER ASPIRATOR BOTTLE 
-AMMOMIACAL SOLUTION 
-RUBBER TUBING 



SPECIAL FLASK, 



COPPER MESH 
(1 LB. REQUIRED) 




Davis Bournonville Institute 



Fig. 4. apparatus for determining chemical 
purity of oxygen 



10 



of commercial electrolytic cells has resulted only from a costly 
process of experimentation. 

The illustration shows the Davis-Bournonville 1000- 
ampere electrolytic generator. This generator, which operates 
with a current of two volts and 1000 amperes generates or 
separates, theoretically, 7.92 cubic feet of oxygen and 15.84 
cubic feet of hydrogen an hour. In some installations the 
hydrogen is not used and it is allowed to escape to the 
atmosphere. The oxygen is drawn off into a gasometer from 
which it is pumped with a water-cooled air compressor into 
cylinders or into a distributing pipe for use in the factory. 
If the hydrogen is also to be saved, it is also collected in a 
separate gasometer and pumped into cylinders or piped to the 
factory for use. 

Inasmuch as hydrogen is somewhat more effective as a 
■preheating gas in the cutting torch for cutting thick steel than 
acetylene it is obvious that the manufacturer, making con- 
siderable use of cutting torches, could advantageously provide 
the comparatively simple apparatus for manufacturing both 
gases required for cutting. 

Pure Water Required for the Electrolyte 

It will not do to use water drawn from the city mains for 
the electrolyte of the generator. Pure water must be provided. 
By this we mean distilled water which, by the process of 
distillation has been freed from earthly impurities, nitrates 
and other compounds that have an injurious effect on the 
electrolytic cell. But although we provide pure water we do 
not use it in the pure state for the reason that pure water 
is not a good conductor of electricity. In order to make 
the cell operate satisfactorily we must introduce into the water 
a chemical that increases its electric conductivity but which 
at the same time has no injurious effect on cell parts. Caustic 
soda has been found to work satisfactorily and it is used for 
this purpose. It has no injurious effect on the plates or con- 
tainers and it remains in the water unchanged indefinitely. 
In short, a cell once charged with water and the proper 
proportion of caustic soda requires only the addition of dis- 

11 



tilled water from time to time, as the caustic soda is not 
used up. 

The cells must be insulated and the pipes connecting them 
to the manifold are provided with short sections of hard 



r^ ^ r 



ASPIRATOR BOTTLE - 



COMBUSTION PIPETTE^ 
PLATINUM SPIRAL- 




-ASFSBATOSt BOTTLE 



TO ELECTRIC SUPPLY 



ABSORPTION PIPETTE 
NG CLAMP 



■^100 C.C. D.B. BURETTE 



__5/i6 RUBBER TUBING 



Davis Bournonvllle Insl'tute 



Fig. 5. apparatus for determining chemical 
purity of hydrogen 

12 



rubber or rubber tubing interposed for insulating purposes. 
The matter of insulation and short circuits is highly important, 
and care must be taken that nothing is laid on the cells that 
might short circuit the bus bars. It is also important that the 
electrical connections are always kept tight and free from 
corrosion. The same remarks apply to the 500-ampere cell 
which is of the same design and construction as the 1000- 
ampere cell. The production of oxygen and hydrogen is just 
one-half of that produced hourly by the 1000-ampere cell. 

Electrolytic cells are set up in batteries connected in 
series and in parallel depending on the number required to 
produce the quantity of gases needed. Suppose that a con- 
stant supply of 40 to 45 cubic feet of oxygen is needed hourly. 
Then six 1000-ampere cells will be required to produce the 
oxygen, if operated steadily. They should be connected in 
series, and as the voltage required for each cell is two volts, 
a voltage of 12 volts will be required to operate the six cells 
in series. 

The apparatus required for operating an electrolytic gas 
generator is fully automatic in practice. The chief duties 
of an attendant are to supply the distilled water daily and to 
make an occasional sample test of the purity of the gas in 
order to be sure that everything is proceeding satisfactorily. 
The motor-generator operates on any commercial current, 
direct or alternating and generates the required low volt- 
age direct current. The electrical apparatus stops and 
starts the gas compressor as the pressure falls and rises. If 
the oxygen is distributed through the building by a pipe line 
the compressor automatically maintains the pressure to which 
the controller is set. If the gases are to be bottled they are 
stored in a gasometer and pumped into cylinders at set 
intervals. 

The distilled water should be supplied daily and in amount 
depending on the production of gases. Approximately, one 
gallon per 100 cubic foot of oxygen at atmospheric pressure 
is required. The oxygen generated by the electrolytic process 
has an average purity of 99^ per cent while the hydrogen^ — 
two times the volume of oxygen — is practically 100 per cent 

13 



or absolutely pure. The purity of the gas is a very important 
factor in the efficiency of the cutting torch,; hence, electrolytic 
oxygen and hydrogen are most efifective gases for the cutting 
torch. 

Questions 

1. About what proportion of the atmosphere is oxygen? 

2. Is oxygen otherwise found in the free state? 

3. What are the three principal methods of producing 
commercially pure oxygen? 

4. Are chemical processes of producing oxygen now 
commercially profitable? Why? 

5. Briefly, what is the liquid air process? 

6. How is oxygen furnished to the trade? 

7. What is the pressure in pounds to the square inch in 
an oxygen cylinder when received from the manu- 
facturer ? 

8. What gases are produced by the electrolytic process? 

9. From what is oxygen produced in the electrolytic 



process 



10. What is the oxygen capacity per hour of a 
1,000 ampere Davis-Bournonville electrolytic gen- 
erator? 

11. Is it safe to distribute oxygen throughout a factory 
in iron pipe? 

12. What precaution should be taken in regard to the 
use of oil and grease in oxygen apparatus? Why? 

13. What is hydrogen used for chiefly? 

14. What is likely to happen if oxygen cylinders are 
stored in a warm place near furnaces, boilers, etc.? 

15. How should the cylinder stop valve be opened to 
prevent leakage around the valve stem? 

16. Is it safe to let an oxygen cylinder stand beneath 
a line shaft or countershaft? Why? 

17. What should be done with the valve protecting cap 
when the cylinder is returned to the manufacturer? 

18. Is it safe to use an acetylene regulator on an oxygen 
pipe line? 

14 



Notes 



15 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING aisd CUTTING 

COURSE OF INSTRUCTION 



Lecture 

ACETYLENE 
AND ACETYLENE CYLINDERS 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 




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ACETYLENE 
AND ACETYLENE CYLINDERS 

Acetylene from Calcium Carbide — Acetylene an Endothermic Compound — 
Acetylene Absorbed in Acetone — Construction of Acetylene Cylinders — Cylinder 
Stop Valve — Danger of' Leaky Pipes and Connections — ^To Find the Amount of 
Acetylene Remaining in a Cylinder — Importance of Maintaining Acetone Content — 
Recharging Acetylene Cylinders — Care of Cylinder Stop Valves. 

In 1892 Thomas L. Willson conducted an experiment at 
Spray, N. C, with an electric furnace for the purpose of pro- 
ducing metallic calcium. He subjected a mixture of coal, tar 
and lime to an electric current of 2000 amperes and 36 volts 
in a Heroult furnace. The temperature produced in the elec- 
tric furnace is very high, and some chemical changes take 
place at high temperatures that are impossible at a lower 
temperature. Willson hoped that the re-action of the mixture 
subjected to the high temperature might produce metallic 
calcium. But he produced a substance of much greater value — 
although he was at first bitterly disappointed. 

Acetylene from Calcium Carbide 

When the furnace was opened it was found to contain a 
dark-colored mass which on cooling was solid and brittle. 
This clearly was not metallic calcium, and in disgust the 
Willson engineers broke it up and threw it into a nearby 
stream. Bubbles of gas were soon noticed rising from the 
fragments at the bottom of the stream, and someone applied 
a match to one of the bubbles as it escaped from the water. 
It burned with a bright but smoky flame — quite different 
from hydrogen flame or any other combustible gas that the 
world was then familiar with. 

An analysis of the furnace product proved it to be calcium 
carbide. Calcium carbide was not unknown to chemists, but 
it had never before been produced in quantities nor was its 
great commercial possibility realized. The electric furnace 
made available a new product with which in a comparatively 



simple apparatus, a gas of astonishing possibilities could be 
cheaply produced. Calcium carbide, like calcium oxide (quick 
lime), slakes in water. When calcium carbide is thrown into 
water it absorbs water and produces slaked lime and acety- 
lene. The slaked lime settles to the bottom while the gas 
escapes from the water and passes off into the atmosphere 
or a suitable receptacle like a gasometer, where it is stored 
for use. 

Acetylene an Endothermic Connpound 

Acetylene is carbon and hydrogen chemically united and 
is very rich in British heat units. In other words, it will 
produce a very hot flame when burned with the proper oxygen 
supply. It is the fuel used in the oxy-acetylene torch, and 
as has been stated in a previous lecture, the discovery of 
acetylene was a step in progress that made gas welding the 




Davis Bournonville Institute 



FIG. 



ACETYLENE PRESSURE REGULATOR AND HIGH AND 
LOW PRESSURE GAUGES 



important industry that it is today. It may be manufactured 
in an acetylene generator for use in the factory or it may be 
purchased, compressed into steel bottles the same as oxygen. 



But unfortunately, acteylene cannot be as safely compressed 
in the same way as oxygen, hydrogen and other gases. It 
is what is called an endothermic or heat-absorbing substance, 
having the peculiarity of absorbing heat when it is generated. 
The atoms in the molecule are in an unstable condition and 
are likely to dissociate under heavy pressure, thus releasing 
molecular heat and causing an explosion. 

Acetylene Absorbed in Acetone 

This peculiarity of acetylene makes it dangerous to com- 
press free acetylene to a pressure much more than 30 pounds 
to the square inch into an ordinary container. It is liable to 
explode, with disastrous results. However, we are able to 
accomplish, indirectly what cannot be done directly with 
safety. Acetylene dissolves freely in acetone. This product 
of wood distillation will absorb over twenty-four times its 
volume of acetylene at atmospheric pressure and ordinary 
temperature, and its absorptive capacity increases directly as 
the pressure rises. At two atmospheres pressure a given 
volume of acetone absorbs over forty-eight volumes of acety- 
lene, and so on. Hence, we can dissolve our acetylene in 
acetone, and by compression force a large quantity into a 
small space. 

But the acetone slightly increases in bulk as it absorbs 
acetylene, and as it gives the acetylene off it shrinks. This 
means that if we have an ordinary steel cylinder filled with 
acetone, containing dissolved acetylene at a pressure of say 
225 pounds to the square inch, a safe condition would exist 
only while the full pressure of acetylene is maintained. As soon 
as any acetylene is drawn off the acetone shrinks and leaves 
a space at the top of the cylinder in which free acetylene will 
collect under heavy pressure. This immediately becomes 
dangerous and likely to explode from shock or even rapid 
discharge of the cylinder contents. 

Construction of Acetylene Cylinders 

The difficulty is overcome by filling the cylinder with a 
porous mixture consisting of charcoal, infusorial earth, as- 



bestos and a small quantity of cement. This mixture though 
compacted until solid, is highly porous and capable of absorb- 
ing a large amount of acetone. The porosity is from 75 to 80 
per cent of the total bulk. It is thus a sort of sponge for the 
liquid acetone. The cylinder is packed completely full, and 
slowly dried and baked. The air is then exhausted to about 
9 pounds absolute and the cylinder is charged with 
acetone, which fills the pores. Then the acetylene may be 
pumped in safely to a pressure of 225 pounds per square 
inch or more, and discharged with equal safety. The porous 
filler co.mpletely fills the cylinder and there are no large spaces 
in which free acetylene can collect. So long as it is prevented 
from collecting in considerable volume in the free state no 
danger need be feared. The filler thus becomes a mineral 
sponge filled with a liquid sponge which absorbs the gas. 

The illustrations show sectional views of a dissolved 
acetylene cylinder, and the principle of the filling apparatus. 
Great care must be taken to fill every part so that no settle- 
ment will take place while in use. The cylinder is jounced 
on a platform that is kept in rapid vibration while the filler 
is being put in. It is necessary to fill the cylinder completely 
up to and including the neck, which is no easy operation. Not 
a cubic inch should be left between the filler and the valve 
nipple. After the filler has hardened a hole is drilled into it 
and filled with an asbestos wick. This provides for drawing 
ofif the acetylene through a considerable size outlet from the 
filler. 

The acetone gives up the acetylene readily when the 
pressure is reduced, and there is little tendency for it to go 
over with the escaping gas unless the rate of discharge is too 
high. If the acetylene is used too rapidly the acetone will 
also be drawn out with injurious effect on the welded joint. 
The escape of acetone can be quickly detected by the odor. 
No trouble will be experienced with escaping acetone in 
ordinary welding when using regular commercial cylinders 
provided the cylinders are kept in a vertical position. If 
necessary to lay the cylinders down they should be supported 
at an angle with the nozzle as high as possible. 



Cylinder Stop Valve 

The view at the lower left, Fig. 1, shows the construction 
of a stop valve used on one make of acetylene cylinders. It is 
quite different from that of an ordinary stop valve used for 
controlling pressvires, and you should study it so that in case 
it is necessary to take one apart you can assemble it properly. 
The stem is round and flattened on one side. This makes the 
use of a special key necessary, and thus prevents tampering 
by unauthorized persons. The valve stem cannot be turned 
except with the key. The collar around it prevents the use 
of a pipe wrench. 

The lower end of the stem sets in a shoe which rests on 
a stack of thin steel discs separated by a thin sheet steel ring. 
Beneath the discs is a perforated disc, containing live holes, 
four in a circle and one in the center. The holes in the circle 
are directly over a circular groove which is tapped by a hole 
leading to the outlet. When the stem is screwed down the 
discs are forced firmly together and the lower one seals the 
opening in the center of the perforated disc. Screwing the 
stem out releases the pressure on the discs and permit the 
gas to escape to the center hole beneath the discs down 
through the holes into the circular valve and out to the torch. 
A fine mesh wire screen or felt plug is provided beneath the 
cylinder stop valve to prevent scale, earth and other foreign 
matter being drawn out with the gas. Small particles of 
scale might lodge in the valve and prevent it being tightly 
closed when the gas is shut off. 

The cylinder valve is double seated, the same as the 
oxygen cylinder valve, to prevent the gas leaking around the 
stem. The valve stem should therefore be opened full or as 
far as the stem can be turned, when in use. The upper seat 
then prevents the gas getting to the stem and leaking. 

Danger of Leaky Pipes and Connections 

Acetylene cylinders are provided with a safety plug 
which is screwed into the shell beside the stop valve. Its 
purpose is to relieve the contents in case of over-pressure. 



If a cylinder is exposed to high temperature for a considerable 
period the pressure may run up to a dangerous point and 
the safety valve is required to relieve the pressure. Acetylene 
cylinders should never be stored near boilers or furnaces nor 
should they be left outdoors in the summer exposed to the 
hot rays of the sun. If the safety valve blows outdoors 
nothing worse is likely to happen than the loss of acetylene, 
but the blowing of the plug in a closed room near a furnace 
may cause a disastrous fire. 

This brings up the matter of leaky pipes and connection, 
which could never be tolerated, as a leak in any acetylene 
apparatus may be a grave danger. An accumulation of acety- 
lene in a closed room becomes highly explosive if the gas 
dilution is slightly in excess of 3 per cent. A spark produced 
by a nail in a shoe heel even may serve to ignite and cause 
an explosion of sufficient force to wreck a building and kill 
the occupants. No pains should be spared to prevent leaks, 
nor should there be any delay in stopping leaks that develop 
in service. Fortunately, acetylene has a peculiar and quickly 
recognized odor somewhat like garlic, which even in minute 
quantities is perceptible to any one with normal perception 
of odors. Explosions resulting fro'm leaky acetylene pipes 
are rare because very few would continue to endure the odor 
long before the mixture has reached the dangerous or ex- 
plosive stage. A great danger is incurred when entering a 
closed room with open lights if the air is contaminated with 
acetylene. Under no circumstances should a fire or any other 
open light be carried into any closed space where the odor 
of acetylene is very strong. It is hardly necessary to caution 
an intelligent person against the danger of exploring a leaky 
pipe with a torch or lighted match to find a leak. Use the 
senses of hearing and smelling to find the leak, or if it is 
minute apply soapsuds to the joints with a brush and watch 
to see bubbles form. 

To Find the Amount of Acetylene Remaining 
in a Cylinder 

Because the gas in an acetylene cylinder is dissolved in 
acetone the pressure gauge is not an indication of the amount 



of gas remaining. The pressure indicated in an oxygen or 
hydrogen cylinders tells you how much gas remains, but not 
so in an acetylene cylinder. The way to tell how much acety- 
lene remains is to clean off the cylinder and weigh it on accu- 
rate scales. Compare the weight with the weight stamped 
on the name plate. The difference is the weight of the 
acetylene contained, provided the acetone content is up to 
the standard. Acetylene under atmospheric pressure and 
normal temperature is rated commercially at 14^ cubic feet 
per pound. Suppose that the cylinder is found to weigh 211 
pounds and the stamped weight is 207 pounds, then the dit- 
ference or four pounds should be the weight of the dissolved 
acetylene. Multiplying 14^ by 4 gives 58 cubic feet, the 
amount of gas still remaining. 

Importance of Maintaining Acetone Content 

If acetylene is discharged rapidly from an acetylene 
cylinder, the acetone is drawn out also because of the rapid 
bubbling of gas and consequent vaporization of the liquid. 
The rule is to never draw from an acetylene cylinder at a 
rate of more than one-seventh of the capacity in cubic feet 
per hour. Suppose that the rated capacity of an acetylene 
cylinder is 225 cubic feet. Then the maximum hourly rate 
of gas consumption should not exceed 32 cubic feet. The No. 
7 tip, if used continuously, is rated at 33 cubic feet acetylene 
consumption, or slightly more than one-seventh of the rated 
capacity of the 225-cubic foot cylinder. However, the cylinder 
should not be overtaxed to supply a No. 7 tip in ordinary 
welding usually as the use of gas is almost always inter- 
mittent. 

Recharging Acetylene Cylinders 

Inasmuch as there is always uncertainty as to the acetone 
content when a cylinder is returned to the recharging station 
it should be weighed and the acetone content checked up. 
If below weight sufficient acetone should be injected to bring 
the weight up to the standard. Then the cylinder may be 
recharged safely to the standard pressure, but not otherwise. 



If the acetone content is not standardized there is no way of 
knowing how much acetylene can be safely charged into the 
cylinder. If a cylinder is returned to the charging station 
containing 40 or 50 pounds pressure, it will be necessary to 
discharge the gas into a gasometer before testing the weight. 
If the charging station is connected with a manufacturing 
plant, however, and the man in charge keeps an accurate 
record of all the cylinders in his care he may ignore the rule 
to recharge and weigh all cylinders at every recharging, pro- 
vided he knows the conditions of use and makes it an in- 
variable rule to test periodically, say at every fifth or sixth 
charging. If this procedure is followed each cylinder should 
be tested with the pressure gauge and the pressure chalked 
on each cylinder. Then when connected to the manifold for 
recharging the following order should be observed in opening 
the charging valves. Suppose that four cylinders are to be 
charged and that the tests show pressures remaining of 15, 
25, 38 and 45 pounds. These numbers are chalked on the 
respective cylinders. When the compressor is started the 
cylinder marked 15 is charged first and the stop valve of the 
cylinder containing 25 pounds pressure is opened only when 
the compressor gauge shows 25 pounds pressure. This order 
should be observed throughout. The reason for it is to pre- 
vent the cylinders containing comparatively high pressures 
charging back into the cylinders containing gas at low 
pressures at so rapid a rate that the acetone is drawn over. 

Care of Cylinder Stop Valves 

The cylinder stop valves on acetylene and oxygen 
cylinders are protected in transit by rail with a metal cap or 
shield that screws over the end of the cylinder nozzle, covers 
the valve and prevents it being broken ol¥. The welder should 
always replace the valve protectors when transporting acety- 
lene cylinders and oxygen cylinders to field jobs or even if he 
is moving them from one part of the plant to another. It is, 
of course, necessary to remove the regulators before the cap 
can be screwed in place. But this is always advisable when 
cylinders are being shifted on a truck. A regulator is easily 

10 



broken and no chances should be taken to save the few minutes 
required to unscrew the connections and replace it when set- 
ting up again. 

Questions 

1. When was acetylene commercially discovered? 

2. In view of the fact that acetylene had long been 
known, why was this a commercial discovery? 

3. How is acetylene generated? 

4. By what process is calcium carbide manufactured ? 

5. Is it safe to compress acetylene to a pressure of more 
than 30 pounds? Why? 

6. What is the recommended safe pressure? 

7. What is acetylene composed of? 

8. How is acetylene safely compressed to 225 pounds 
per square inch? 

9. What is the chief characteristic of the filler used in 
acetylene cylinders? 

10. What is the liquid used to dissolve the acetylene? 

11. What happens if you use acetylene too rapidly? 

12. Is acetone injurious when welding? 

13. Can you determine how much acetylene remains in 
a cylinder by weighing it? 

14. How many cubic feet in one pound of acetylene at 
atmospheric pressure? 



Copyright 1919 by thh; 
Davis-Bournonvilx^e Company 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

ACETYLENE GENERATORS 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonville Company 



ACETYLENE GENERATORS 

Commercial Acetylene Generators — Generator Types — Principal Requirements 
of Generators — Davis-Bournonville 200-Pound and 300-Pound Generators — Acety- 
lene Generator House — Directions for Charging — Rules for Recharging — Safety 
Rules. 

•The generation of acetylene from calcium carbide is very 
simple, in fact, so simple that it was discovered by accident ; 
and the experiment can be made by anyone having a lump 
of calcium carbide and a glass of w^ater. Drop the carbide 
into water and immediately bubbles of gas begin to rise which, 
if ignited, burn with a red, smoky flame as they come to the 
surface. That, you may know, is what happened when Will- 
son undertook to produce metallic calcium in 1892, but 
obtained calcium carbide instead. The rejected mass result- 
ing from the failure produced an unknown gas when thrown 
into a nearby stream. Someone with an investigating spirit, 
undaunted in the face of apparent failure, discovered that a 
new means of producing a combustible gas had been created. 

Commercial Acetylene Generators 

While it is true that the apparatus needed for the labora- 
tory experiment to make acetylene is very simple, the 
commercial generation of acetylene is far from being a simple 
matter. In the first place, acetylene is a good servant but a 
bad master. Under normal conditions it performs beauti- 
fully, but if mishandled the results may be disastrous. 

The apparatus required for the commercial generation of 
acetylene should be efficient, safe and automatic in operation 
and convenient to take care of. Such generators are available, 
but they were developed only after much experimenting and 
costly mistakes. There are, available today acetylene genera- 
tors that require so little attention that they are practically 
automatic and so safe that there is little difficulty in getting 
permission to use them for factories in towns and cities. 



Generator Types 

There are two systems or types of generators, differ- 
entiated chiefly by the manner in which the water and car- 
bide are brought together. One called the water-to-carbide 
type, is that in which the water is applied to the carbide by 
sprinkling or injection. The other and principal type of 
acetylene generator is the carbide-to-water type, in which a 
comparatively large body of water is provided and means for 
dropping the carbide into the water automatically and in 
amounts determined by the consumption. The carbide-to- 
water type of generator has certain advantages that recom- 
mend it to users in general as well as safety engineers and 
insurance companies. A large volume of water is provided 
in this type to absorb the heat produced when the carbide 
slakes and gives off gas. The water "drowns" the carbide 
and prevents the temperature rising to a dangerous point. 
It is obvious that as long as the carbide is under water the 
temperature cannot rise above the boiling point or 212 degrees 
F. Cool generation is an imperative requisite for safe and 
efficient generation. 

Acetylene is an endothermic compound and is liable to so- 
called spontaneous explosion under certain conditions such 
as high compression, overheating, the presence of impurities, 
sudden shock, etc. The subject of safety, therefore, looms 
large in the consideration of an acetylene generator, and it is 
desirable to outline the principal requirements of a generator 
that meets the insurance requirements as well as the require- 
ments of the commercial users. 

Principal Requirements of Generator 

1. It should provide for automatic generation of gas, 
and at no time should the temperature rise above the 
boiling point of water. 

2. A safe generator should produce at no time an ex- 
plosive mixture of acetylene and air. 

3. It should be so constructed as to be positive in opera- 
tion and should be well built of lasting materials. 



4. The mechanism should be simple and not likely to 
get out of order. Generators are required to work 
automatically and are likely to be attended by un- 
skilled labor. They should, therefore, be absolutely 




\ Davis Bournonville Inslltule 



Fig. 1. DAvis-BOURNONviLLE NO. 200 (and no. 300) 

ACETYLENE GENERATOR 



reliable and easily understood by men of limited 
mechanical knowledge. 

5. The insurance underwriters require that acetylene 
generators must operate with a comparatively low 
pressure. The pressure should never exceed 20 
pounds per square inch, and in general should be 
somewhat less than 15 pounds. 

6. The generator should be so constructed that it is 
easily cleaned and recharged. The construction 
should be such that little gas escapes when cleaning 
and recharging, and no explosive mixture is pro- 
duced when it is again started into operation. 

7. Safety devices should be provided to prevent over- 
pressure. 

Davis-Bournonville 200-Pound and 300-Pound 
Generators 

The illustration shows the construction of the Davis- 
Bournonville acetylene generator of the 200-pound and 300- 
pound sizes. It is of the carbide-to-water type, a large reser- 
voir for water being provided in the base and a weight motor 
for feeding the calcium carbide automatically to the water, as 
required. The carbide falls from the hopper upon a rotating 
feeding disc from which it is slowly scraped off to fall into 
the water beneath. The operation of the feed mechanism is 
controlled by the pressure of acetylene in the generator. When 
acetylene is being generated faster than it is used the pressure 
rises, and when it has reached a certain limit — generally 10 
to 12 pounds maximum for welding and cutting — the opera- 
tion of the motor is stopped and the rotation of the feeding 
disc ceases. 

The carbide sinks to the bottom and slakes, giving off 
acetylene which bubbles to the top and finally escapes through 
the backfire valve and filter to the outlet service pipe. The 
capacity rating of the Davis-Bournonville generators is ex- 
pressed by a number. The No. 200 generator holds 200 pounds 
of calcium carbide in the hopper and generates 200 cubic feet 
of acetylene hourly. The water reservoir contains 200 gallons, 



thus providing one gallon per pound of carbide. On the basis 
of 43/2 cubic feet of acetylene generated from one pound of 
carbide, the No. 200 generator will produce 900 cubic feet of 
gas at atmospheric pressure from one charging. 

The motor is driven by the weight X acting through the 
cable upon the drum of the motor A. An interference clutch 
or stop checks the motor when the pressure runs too high, 
being operated by a feed controlling diaphragm. The calcium 
carbide is stored in the hopper from which it drops to the 
feeding disc N. To prevent clogging and stoppage a floating 
displacer ring O is provided. This is suspended so that it is 
free to swing to one side or the other in case a lump of car- 
bide too large to pass through the feed mechanism falls upon 
the feeding disc. 

The spent carbide or residuum collects in the bottom of 
the reservoir in a compact, sticky mass which requires break- 
ing up and agitating in order to discharge it to the lime pit 
when recharging the generator. An agitator operated by a 
crank outside the shell is provided for the purpose. The mass 
of water and lime stirred up with the agitator runs ofif to the 
pit when the connection valve is opened. One of the rules 
never to be broken is to discharge the slaked carbide from 
the generator at each recharging. If the residuum is allowed 
to remain it reduces the water capacity and may cause over- 
heating and polymerization. The development of polymers 
is injurious to the acetylene and it reduces the amount gen- 
erated from the carbide. Polymerization is indicated by the 
presence of yellow tarry deposits on the residuum. 

In case of over-pressure developing the gas blows off and 
escapes through the vent pipe V to the atmosphere. The 
v^ent pipe is connected to the water seal or trap on the side 
of the generator. This trap fills a double function. It pro- 
vides for the overflow of water from the generator when re- 
charging. The reservoir cannot be filled above the level of 
the out-flow pipe. The second function is to give warning 
of stoppage in the vent pipe should one occur. The gas 
escaping through the blow-off valve then forces the water 
seal and escapes. The odor of acetylene prevading the 
premises gives notice that something is wrong. 

7 



Generator Parts 

A. Motor drum for weight cable. 

B. Carbide filling plugs. 

C. Backfire or flashback chamber. 

D. Emergency locking collars. 

E. Lever on feed controlling diaphragm valve, 

F. Lever of emergency diaphragm valve, v^^hich operates 
emergency locking collars D. 

G. Feed controlling diaphragm valve. 
H. Emergency diaphragm valve. 

J. Main shaft driving carbide feed disc. 

K. Generator shell. 

L. Generator top plate. 

M. Carbide hopper. 

N. Carbide feed disc. 

O. Carbide displacer ring. 

P. Backfire or flashback chamber valve and float. 

Q. Outlet pipe to backfire or flashback chamber. 

R. Overflow plug of backfire or flashback chamber. 

S. Filter. 

T. Water filling pipe for backfire or flashback chamber. 

U. Pressure gauge bushing. 

V. Blow-off pipe. 

W. Outlet pipe to gas service line from generator. 

X. Operating weight. 

Y. Vertical controlling rod. 

Z. Motor locking thumb pin. 

Aa. Vent valve. 

Bb. Handle of vertical controlling rod. 

Dd. Water filling funnel. 

Ee. Valve in water filling pipe. 

Ff. Water filling pipe of generator. 

Gg. Overflow pipe of drainage chamber. 

Hh. Lever of blow-off valve. 

li. Residuum discharge valve. 

Jj. Handle of agitator. 

Kk. Valve in outlet pipe to backfire or flashback chamber. 



LI. Generator blow-off valve. 

Mm. Backfire chamber blow-off valve. 

Nn. Charging platform. 

Oo. Residuum gutter. 

Qq. Residuum discharge pipe. 




BLOW OFF VALVE L I 



FEED CONTROLLING 
DIARHRSGM VALVE G 



EMERGENCY DIAPHRAGM VALVE B 



Fig. 2. top of davis-bournonville no. 200 (and no. 300) 
showing motor and control valves 



Xx. Blow-off pipe from flashback. 
Yy. Motor interference pin. 

Acetylene Generator House 

Acetylene generators may be placed within an isolated 
building, preferably of fireproof construction. It should be 
located away from boilers, furnaces, railway tracks or any 
source of fire or sparks. The fact should be recognized th?' 
an acetylene generator is used to produce an inflammable gas 
which, mixed with air, becomes highly explosive and danger- 
ous. A generator may be placed within a building used for 
other purposes provided it is isolated by partitions and the 
room is vented to draw off any accumulation of gas. Pre- 
ferably the generator room should be so located that artificial 
heat will not be required in the winter to prevent the water 
from freezing. But if this is not feasible a steam coil or radi- 
ator may be provided for use in extremely cold weather. 
While it is true that a generator in use is not likely to freeze 
because of the heat produced in generation, no chances should 
be taken of a generator freezing when not in use as the result 
may be serious. 

Inasmuch as the conditions are generally such that the 
residuum cannot be discharged into the sewer it will be nec- 
essary to provide a pit adjacent to the generator house into 
which it can be deposited. In some localities the slaked lime 
has commercial value and can be sold at a price sufficient to 
pay a profit on the cost of handling and selling. 

Open lights should never be used in an acetylene gener- 
ator house. Incandescent lights should be provided, but all 
switches should be placed outside. The light bulbs should 
be protected by gas-tight glass. Incandescent bulbs attached 
to flexible cables provided with wire protectors may be used 
for examining the generator when absolutely necessary. The 
use of such lights, however, should be limited to emergencies, 
as, there is always danger of short circuits, broken bulbs or 
other accidents that might cause ignition of inflammable gas. 

Copper pipe or tubing should never be used for an acety- 
lene pipe line, as the acetylene may, under favorable condi- 

10 



tions form copper acetylide, which is an explosive compound. 
Brass (which contains copper) is not so affected except when 
in contact with the sludge formed in an acetylene generator. 
No brass parts should be used in a generator that make coii- 
tact with the water. Brass parts in the generator above the 
water exposed only to the gas itself are not likely to be affected. 

Directions for Charging 

I. Close the vent valve Aa by turning the handle Bb 

to the left as far as it will go. This releases the 
motor interference pin Yy. 

2. Release the motor by means of the motor locking 
thumb pin Z and raise the lever on the feed con- 
trolling diaphragm valve, thus allowing the weight 
to descend a short distance in order to determine 
whether the motor is operating properly. Then 
rewind to the full height and lock with the motor 
locking pin. 

3. Open the vent valve Aa by turning the handle Bb 
to the right as far as it will go. 

4. Close the residuum valve li. 

5. Open the water filling valve Ee. 

6. Close the valve Kk in the outlet pipe to the flash- 
back or backfire chamber. 

7. Remove the out-fiow plug R from the flashback 
chamber C and the plug from the water filling pipe 
T. Fill with water at the lower opening until it 
overflows at R and then replace both plugs tightly. 

8. Fill the generator with water through the funnel Dd 
until it overflows at Gg, then close the valve Ee. 

9. Remove the carbide filling plugs B and fill the 
hopper with 1^-inch by ^-inch carbide (nut size). 
Replace the carbide filling plugs tightly. 

10. Close the vent valve Aa by turning the handle Bb 
to the left as far as it will go. 

II. Unlock the motor thumb pin Z. 

12. Raise the feed control diaphragm lever, allowing the 
motor to run until the valve shows about 5 pounds 

11 



pressure. Then raise the lever Hh of the blow-off 
valve LI and discharge the gas until the pressure 
has dropped to 2 pounds. This is done to remove 
all air from the generator and avoid producing an 
explosive mixture of air and acetylene. Again raise 
; the feed control diaphragm lever and permit the 

generator to operate until the gauge shows 8 pounds 
pressure, after which the motor will operate auto- 
matically as the gas is consumed. 
13. When ready to use acetylene, open the valve Kk 
slowly and thus admit the acetylene to the service 
pipe through the backfire chamber and filter. 

Rules for Recharging 

The rules for recharging the generator dififer somewhat 
from those for charging and starting, as follows : 

1. Close the valve Kk in the outlet pipe to the backfire 
or flashback chamber. 

2. Close the vent valve handle Bb to the right as far 
as it will go. 

3. Revolve the agitator handle Jj several times. 

4. Open the residuum discharge valve li and draw off 
all the water and sludge, after which the valve should 
be closed. 

5. Open the water inlet valve Ee thereafter, fill the 
generator with water. Revolve the agitator again 
and draw off all water and sludge as before. 

6. Having closed the valve li, fill the generator with 
water at the funnel Dd until it overflows at Gg. (It 
is desirable when filling to let the water run in as 
rapidly as possible in order to keep the filling pipe 
full and thus prevent air entering the chamber at 
the same time.) 

7. Close the valve Ee in the water filling pipe. 

8. Rewind the motor and lock it with the motor lock- 
ing thumb pin Z. 

9. Remove the carbide filling plugs B and fill the 
hopper with l^^-inch by ^-inch carbide (nut size). 

12 



Replace the filling plugs. 

10. Close the vent valve Aa by turning the handle Bb 
to the left as far as it will go. 

11. Unlock the motor thumb pin Z. 

12. Raise the feed controlling diaphragm lever, allowing 
the motor to run until the gauge shows about 5 
pounds pressure. Then raise the lever Hh of the 
blow-off valve LI and discharge the gas through the 
vent pipe until the pressure has dropped to 2 pounds. 
This is done to remove all air from the generator. 
Again raise the feed control diaphragm lever until 
the gauge shows 8 pounds pressure, after which the 
motor will operate automatically as the gas is con- 
sumed. 

13. When ready to use the acetylene, slowly open the 
valve Kk. 

Safety Rules 

1. Remember that an acetylene generator produces in- 
flammable gas and that all precautions should be 
taken to prevent the escape of gas through careless 
handling of apparatus, leaks, etc. 

2. Do not carry or permit lighted pipes or cigars or 
open fires of any kind within a generator house or 
room. 

3. Always remove all the, residuum that is clogged in 
the bottom of the generator and fill with fresh water 
before recharging. Neglect of this rule may cause 
the generator to be seriously overheated. In such 
an event do not open the generator until it has cooled 
down, as the admission of air to the heated gas may 
cause trouble. If through neglect a generator be- 
comes overheated stop its operation and play a 
water hose upon it until it has cooled down. 

4. Make sure that all the joints and pipes are tight 
before operating the generator. Joints may be 
tested for leaks by applying soap suds with a brush. 
Never use a light for the purpose. 

13 



5. Never force carbide into the filling openings or fun- 
nel with a metal rod. 

6. Always discharge the air mixture from the generator 
each time it is recharged, as is directed in Rule 12. 

7. After recharging the generator discharge all the air 
mixture from the pipe system before lighting 
torches. A back pressure valve should be provided 
in the pipe system, however, to prevent the escape 
of acetylene when recharging and thus making this 
precaution unnecessary. 

8. The operating weights fall a certain distance in dis- 
charging the carbide charge in the hopper. If the 
operator notes the position of the driving weight 
when a full charge has been fed to the generator 
he will know thereafter when the charge is nearly 
exhausted by merely noting the , position of the 
weight. 

9. When making repairs to the generator always remove 

the carbide hopper and fill the shell completely full 
of water before applying a welding torch or solder- 
ing iron. Repairs of this nature should not be made 
in a generator house if there are any other generators 
in the same house. 

10. The generator is designed to operate at a pressure 
from 10 to 12 pounds and the blow-ofif valve to 
operate at a pressure of 15 pounds. If for any rea- 
son the blow-off valve should fail the emergency 
diaphragm valve will raise a lever and thereby en- 
gage an emergency locking collar, thus stopping the 
motor. The motor cannot be operated again until 
the gas pressure has been reduced and the cause for 
the excess pressure found and removed. It should 
be understood, however, that the emergency dia- 
phragm valve is designed only for operation in an 
emergency and that it is not likely to go into action 
in the ordinary operation of the generator. 

11. The flashback or backfire chamber C must be kept 
filled with water at all times up to the level of the 
overflow plug R. 

14 



12. Care should be taken when charging a generator 

that no foreign substance is mixed with the carbide. 

A piece of brass or copper getting into the generator 

may cause trouble. 

The generator thus provides for automatic gas production, 

it Hmits the pressure produced and is provided with safety 

devices which prevent careless and dangerous practice in 

charging. Of course, no apparatus can be made foolproof. 

Common sense is required of the one who takes care of a gas 

generator as much as of one who attends a heating furnace. 

[f the rules are followed no trouble should be feared. 

Questions 

1. How is acetylene produced? 

2. What are the principal types of generators? 

3. Which is the best type? Why? 

4. How are generators rated? 

5. Why is a large water capacity desirable in an acety- 
lene generator? 

6. What is the rule for water capacity in an acetylene 
generator? 

7. What precaution should be taken in regard to open 
lights when working around a generator? 

8. Is it safe to use an incandescent lamp? If so, how 
should it be guarded? 

9. What is the function of the clockwork motor? 

10. What should be done with the residuum before re- 
charging? 

11. What is the danger of leaving the residuum in the 
generator? 

12. What should be done when a leak develops? 

13. How would you proceed to find a leak? 

14. What happens if the vent valve becomes obstructed? 



IS 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

OXY-ACETYLENE WELDING 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonvii,x,e Company 



OXY-ACETYLENE WELDING 

What Welding is — Importance of Correct Torch Movement — Importance of 
Holding Welding Torch and Welding Rod in Proper Relation and Position — Desir- 
able Characteristics of Welders — Classes of Welding — Grading Steels with the 
Emery Wheel — Learn to Estimate Costs — Safety Considerations. 

We have lectured about combustion, structure of flame, 
heat and temperature, controlling gas supply, the oxy-acety- 
lene welding torch, and several other matters closely pertain- 
ing to oxy-acetylene torch practice, and you have done some 
Avelding and are beginning to comprehend the possibilities as 
well as the difficulties of the art. We will, therefore, talk 
today about welding in the light of your experience. The 
work you have done in the past few days has helped, no 
doubt, to make clear some of the things that we have harped 
on but which you did not, perhaps, fully comprehend. The 
fact is that a full knowledge of oxy-acetylene torch practice 
requires a knowledge of so many things that it is somewhat 
difficult to start at any really logical place and tell you about 
it. About the best we can do is start you at welding and 
then tell you about the principles as you learn. When you 
are able to apply more or less successfully the principles of 
welding you are more interested in everything that makes 
for progress. 

What Welding Is 

In the first lecture on combustion, welding was defined 
as a process of uniting metals by fusing or partly melting 
the parts to be joined which then flow together and be- 
come one. That is the foundation of oxy-acetylene welding. 
You must fuse the edges of the plates you wish to join, and 
let the fused metal run together. You do not force the metal 
together ; it runs together of its own accord when properly 
fused. The success of the welder depends on how well he 
fuses the metal and how systematically and intelligently he 
goes at his work. It will not do to fuse the metal with a 



carbonizing or oxidizing flame; it must be done in a neutral 
flame in order to prevent injuring the metal and making a 
poor joint. You must learn to make welds with as little de- 
terioration of the physical structure as possible. Remember 
that welds can be made having 90 to 95 per cent the strength 
of the unwelded steel. 

The expert welder must be able to weld cast iron, steel, 
bronze and aluminum ; he should be able to braze all the 
metals including copper, brass, malleable iron and other metals 
that may be brazed more effectively than welded, sometimes. 
He must be able to make the castings ready for welding, 




Davis Boumonville Institute 



Fig. 1. SCARFED JOINT WELD MADE BY THE BLACKSMITH 

bevel the joints, adjust them for alignment and preheat them 
so as to avoid destructive stress on the welded joint after the 
job is done. 

Importance of Correct Torch Movement 

The welder must go through a course of training that de- 
velops manual skill. He has to learn to hold the torch un- 
consciously with the tip of the' white hot cone from an eighth 
to three-sixteenths inch above the puddle and at the same time 



give the torch a motion across the joint that will distribute 
the heat to the best advantage. On prepared joints the welder 
is instructed to give the torch a sort of semicircular zig-zag 
movement. The reason for the semicircular instead of the 
plain zig-zag movement is that the flame dwells longer on 
the margins of the joint where heat must be supplied to com- 
pensate for that lost by conduction and where it is generally 
difficult to obtain sufficient temperature to insure perfect 
fusion and penetration. If the torch tip is given the simple 
straight zig-zag movement the flame will dwell only momen- 




FlG. 2. TORCH HANDLE HELD PARALLEL TO JOINT. INCORRECT 

tarily on the margins. Consequently, the metal will remain 
comparatively cool, and lapping and cold-shuts will likely be 
produced. If, however, the tip is given a semicircular 
movement the flame is concentrated for a considerably longer 
time on the margins of the joint and sufficient heat is thereby 
imparted to produce fusion and union. 

Importance of Holding Welding Rod and Welding 
Torch in Correct Relation and Position 

The accompanying illustrations, Figs. 2, 3, 4 and 5, show 
some of the errors to be avoided in welding as regards the 



direction of welding, position of torch and the melting of the 
adding material. Fig. 6 shows the correct position of the 
torch in relation to the joint and the angle made by the tip 
with the surface of the metal. It also shows the correct 
direction of welding a prepared joint and the proper way to 
hold the welding rod. Prepared joints should be welded from 
left to right with the torch handle held at right angles to 
the joint and the head inclined to the right to an angle of 
about 50 degrees. The welding rod should be held in the 
left hand, and the white hot cone of the flame should never be 
used to melt the rod. It must take its heat from the puddle 




Davis Bournonville Institute 



Fig. 3. welding from right to left in a prepared joint. 

incorrect 

as that is the only way the welder can make sure that he 
is imparting the necessary heat to obtain penetration. 

Fig. 2 shows correct practice as regards the direction of 
welding and the manner of manipulating the welding rod but 
the torch handle is held approximately parallel to the joint. 
This is an awkward constrained position for the welder to 
assume, and should never be permitted except when the sur- 
roundings make it necessary. Fig. 3 shows welding from 
right to left in a prepared joint. It illustrates the disad- 



vantage at which the flame operates on the declivity of the 
weld. The flame is not directed squarely against the side of 
the weld and lapping is likely to result. Moreover, there is 
danger of overheating the bottom of the vee and blowing a 
hole through. The torch should always be held in relation 
to the direction of welding so that the flame is directed more 
or less squarely against the declivity formed by the joint 
material. A left-handed welder may logically weld from right 
to left in a prepared joint as he will hold the torch in the 
left hand and the welding rod in the right. 

Fig. 4 shows welding proceeding correctly from left to 
right in a prepared joint but the torch head is inclined to the 
left so that the flame is not directed squarely against the 




Fig. 4. torch head inclined to left, incorrect 

weld declivity and hence, the same fault is developed as in 
welding from right to left in Fig. 3. The welder must hold 
the torch at the proper angle to develop the best results from 
the flame. To do otherwise is to waste gas and to invite poor 
results. 

You have been repeatedly warned not to fuse the add- 
ing material directly with the torch flame. Fig. 5 shows 
this error as it would appear to one standing in front of 
the weld being made by a left-handed operator. It is ob- 
vious from this illustration that the flame is not being di- 
rected where it should be to produce a puddle of molten metal 
that will blend perfectly with the parent metal. The welder 



is more intent on fusing the welding rod and seeing the drops 

fall. The invariable results of such practice are cold-shuts, laps 
and weak welds. 

Desirable Characteristics of Welders 

The welder should be an all-around type of man who 
combines good common sense, judgment and manual skill 
and who is not afraid to work. It is not sufficient that he 
should be able to weld the casting so that when finished the 
parts will be in line and the shape will be nearly the same 
as before. If the welded casting is so distorted after welding 




Fig. 5. melting adding material with direct flame. 

BAD practice 

that it cannot be used or is an eye-sore, the job is a failure 
no matter how strongly the joint may be made. He must 
be able to choose the proper adding material, and use it 
economically; he should also recognize at a glance when 
flux should be used and what kind will yield the best re- 
sult. If the welder is able to do good sound work, he should 
be able to tell bad work no matter how skillfully it may 
be camouflaged. But avoid knocking. Be generous and give 
others the credit due them. The knocker hurts himself and 
the booster helps every one, himself included. 

8 



We have not, heretofore, said much about preparing joints 
for welding nor have we discussed preheating. Both these 
subjects will be taken up later in detail. We will mention 
them here in order that you can get an idea of the manifold 
requirements of a successful welder. He must not only be 
able to weld but he must be able to prepare for welding, 
line up on floors or surface plates, build up temporary pre- 
. heating furnaces, apply the heat where it will be most ef- 
fective, protect parts that might be injured by overheating, 
learn to do his own rigging; in short he should be a master 
of his trade, able to handle a wide variety of repair work in 
a workmanlike manner. 

Classes of Welding 

Oxy-acetylene repair welding is divided into two general 
classes, shop work and field work. Repair work that can be 
carried to the workshop is, of course, taken where the ap- 
pliances are at hand for lining up and preheating. Work that 
can be taken to the workshop, lined up on the bench or floor 
and welded, generally presents less difficulties than that which 




Fig. 6. correct practice in welding prepared joint. 

PUDDLE melting THE WELDING ROD 



must be done outside or, as we say, in the field. Often it is 
necessary to make a weld on a heavy casting where it lies 
and where rigging must be erected to lift it and turn it over. 
Many field jobs are very difficult, and the job may be in 
a remote region where nothing is available except that which 
the welder takes with him. He must, therefore, learn to 
systematize his business and to prepare for the unexpected 
when he goes to do an outside job. 

The welder should begin his career if possible in the shop 
where the tools and apparatus necessary for successful all- 
around welding are provided. When he has learned to know 
the conditions under which welding can be successfully ac- 
complished in a shop, he will be able to create these con- 
ditions to a larger degree when sent out to do field work. 
The field work will require much more preparation than shop 
work and will often call for a higher range of skill and good 
judgment. Very often, if not usually, the field work is done 
under pressure. A mill or factory may be partly at a stand- 
still because some apparatus has failed. The welder should 
learn to work quickly but without excitement no matter how 
great the emergency or how many are advising him that speed 
is imperative. 

Machine steel, tool steel, steel castings, high-speed steel, 
cast iron and malleable iron have certain well defined char- 
acteristics which the oxy-acetylene welder should be able 
to recognize at a glance. It is important that he recognize 
these metals in order that he will not undertake to do im- 
possible or unprofitable welding. Machine steel is steel low 
in carbon, and it can be welded with ease. Gray cast iron is 
easily welded but malleable iron is a difficult metal to weld 
because of the peculiar heat treatment it goes through in 
order to give it the malleable characteristics. Brazing is 
better than welding. Tool steel and high-speed steel can be 
welded but not by the usual methods. 

Grading Steel with the Emery Wheel 

A simple test for grades of steel is grinding them on an 
emery wheel. The steel high in carbon makes many white 

10 



hot sparks while a low carbon steel throws comparatively 
few. Mushet and high-speed steels when ground, produce 
dull red sparks. It is difficult to describe the characteristics 
of all metals as shown by the grinding test, and the best way 
for the welder to learn them is to take samples of known 
steels, wrought iron, cast iron, malleable iron, etc., and test 
them one after another. A little time spent in this way will 
be well repaid. 

While it is possible to weld almost any metal with the 
oxy-acetylene torch, it is not commercially feasible to do 
certain classes of welding by this process. The welder should 
learn to distinguish between the classes of work that are 
commercially weldable and those which should be undertaken 
only to meet an emergency and which, under ordinary con- 
ditions, could be done more cheaply by other methods. It is 
better for him to reject a proffered job of welding than to 
undertake it when he knows that the result will be unsatis- 
factory to the customer because of the high cost. It is not 
good business to do work that will cause dissatisfaction either 
because of the quality of the work or its ultimate cost. Bar- 
gains are good bargains only when both parties are pleased 
and satisfied. 

Cutting iron and steel with a torch is easily learned. The 
welder, however, should not despise the cutting game. He 
may find it very profitable to do cutting either in an emer- 
gency where the prompt removal of steel debris is neces- 
sary or in preparing for welding. Therefore, the welder 
should be able to use the cutting torch with skill and pre- 
cision. The cutting torch can be used in preparing work for 
welding oftimes at costs far below any other. Suppose, for 
example, you are required to make a frame of angle iron. The 
torch will cut the angles to a 45-degree bevel quickly and at 
low cost. No other tools but the torch will be required ex- 
cept a bevel protractor to lay off the angle. 

Learn to Estimate Costs 

Knowledge of costs of the materials used, comprising 
oxygen and acetylene gases, adding material or welding rods, 

11 



fluxes, etc., is highly desirable. The oxy-acetylene welding 




NO. 738-LARGE STYLE O" TORCH 
MACHINE WELDING 



NO. S13-A LARGE STYLE "o" TORCH 
MACHINE WELDING -WATER COOLED 




Fig. 7. types of welding torches available for all kinds 

OF welding 



12 



business is one that offers large opportunities to the wide- 
awake progressive workman. He can start in business for 
himself with a comparatively small capital. If one goes into 
business for himself he should know the names of concerns 
from which he can obtain the best supplies and should com- 
pare the cost of acetylene in cylinders and of the gas made on 
his own premises with an acetylene generator. 

Safety Considerations 

Safety considerations and care of health are as important 
in the oxy-acetylene welding and cutting business as in any 
other line. The welder often is required to go into danger- 
ous places to do emergency work. He should first of all pro- 
vide suitable spectacles and goggles for protecting the eyes 
and should wear clothes suitable to his trade. Care of ap- 
paratus is imperative both for economy's sake and safety's 
sake. An acetylene cylinder filled with dissolved acetylene is 
commercially safe provided it receives ordinary care. But if 
it is mishandled and allowed to fall over or be struck by 
falling objects, the shell may be ruptured or the regulator 
broken off. It may be argued that this would mean only 
the escape of gas and no particular harm other than the loss 
of the gas and perhaps a shock to the nerves. But that 
is only part of the truth. Escaping acetylene in a closed 
room is exceedingly dangerous. Open lights will fire the 
gas and cause a disastrous fire. The flames may spread so 
quickly that men in the room will be unable to escape with 
their lives. 

In the foregoing we have undertaken to give you some 
idea of thz oxy-acetylene welding business and the require- 
ments of the skillful welder. He has to be a pretty capable 
sort of a man who, first of all, is a good workman but who 
should have some commercial sense that would enable him 
to run a business of his own or to manage a department. 
He must be careful of his men and that means that he must 
be careful of his apparatus and in the methods he follows. 
He should also be careful of his reputation for keeping prom- 
ises and being trustworthy. 

13 



Questions 

1. How does one learn to use the torch? 

2. What is autogenous welding? 

3. What makes a successful weld? 

4. What percentage of weld strength may be reason- 
ably expected in mild steel? 

5. What is the proper torch movement for thin steel? 

6. What movement should be used on all prepared 
joints? 

7. What is the difference in efrect on the two torch 
movements on the parts to be welded? 

8. How should the torch be held in relation to the 
joint? 

9. What kind of a man would you pick to be a welder? 

10. What is the best guarantee of a sound welded 
joint? 

11. Can you tell different grades of steel by grinding 
them on an emery wheel? 

12. What kind of sparks are thrown by high carbon tool 
steel? 

13. How can you identify a malleable casting? 

14. What would you do if required to mend a broken 
malleable casting? 

15. Suppose that oxygen costs 2 cents a cubic foot and 
acetylene 1 cent a cubic foot? What would be the 
cost for gases when using the torch continuously 
with the No. 5 tip for one hour? 



14 



Acetylene and Oxygen Pressures 

Davis-Bournonville Style C Welding Torches 
with Style 99 and 100 Tips 





Thickness 


Acetylene 


Oxygen 


Acetylene* 


Oxygen* 


Tip 


of Metal 


Pressure 


Pressure 


Consumption 


Consumption 


No. 


Inches 


Lbs. 


Lbs. 


Per Hour 


Per Hour 


00 


^Veryl 
\Light/ 


1 


1 


0.6 CU. ft. 


0.8 CU. ft. 





1 


2 


1.0 


1.3 


1 


1 1 


1 


2 


3.2 


3.7 


2 


A" A 


2 


4 


4.8 


5.5 


3 


A-H 


3 


6 


8.1 


9.3 


4 


Ks-M 


4 


8 


12.5 


14.3 


5 


J4-A 


5 


10 


17.8 


21.3 


6 


A-^s 


6 


12 


25.0 


28.5 


7 


1^-^ 


6 


14 


33.2 


37.9 


8 


H-^ 


6 


16 


42.0 


47.9 


9 


^-M 


6 


■ 18 


58.0 


65.9 


10 


M-up 


6 


20 


82.5 


94.0 


11 


/ Extra \ 


8 


22 


89.0 


101.2 


12 


\ Heavy/ 


8 


24 


114.5 


130.5 



Operators frequently adjust the pressure regulators from one to two pounds 
above the figures given in the table to allow for gauge variations and drop of pressure 
when the gases are supplied in cylinders. 

* Gas consumption per hour is the maximum with torch burning continuously. 



15 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

EXPANSION AND CONTRACTION 
PREHEATING 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY. N. J. 



Copyright 1919 by thb 
Davis- BouRNONViLX-E Company 



EXPANSION AND CONTRACTION- 
PREHEATING 

Changes of Temperature Change Length, Breadth and Thickness — Expansion 
Must be Provided for in Welding — Cost of Heat Produced by Torch too High 
for Preheating Use — Preheating Necessary for Large Castings — Setting Up a Cast- 
ing for Preheating and Welding — Preheating a Broken Pulley. Preheating a 
Bronze Valve Seat Casting — General Theory of Preheating. 

Heat is a mode of motion. According to scientific theory 
the molecules of all matter are in a state of vibration or move- 
ment to and fro. The extent of vibration depends on the 
temperature, increasing as the temperature rises, and decreas- 
ing as it falls. According to this accepted theory there is no 
movement or heat vibration at absolute zero. The absolute 
zero or point of no temperature is 273 degrees below the 
freezing- point of water on the Centigrade scale and 459 de- 
grees below the zero point on the Fahrenheit scale. 

Matter exists in three forms — solid, liquid and gaseous. 
At very low temperatures all gases and liquids become solid. 
On the other hand, all solids melt at some temperature; and 
at very high temperatures they become gases. We find water 
in the three forms in nature. It freezes at 32 degrees and 
becomes ice, and boils away in steam or gas at 212 degrees F. 

Changes of Temperature Change Length, Breadth 
and Thickness 

Changes in temperature mean changes of length, breadth 
and thickness. A bar of iron or steel expands as it is heated 
and contracts as it cools. The expansion of a bar of steel 
by heat is attended with great force. It is practically impos- 
sible to prevent a bar expanding with heat, and contraction 
cannot be prevented as it cools. In fact, so great is the 
contraction force that if a long rod is heated and fixed firmly 
in a cast iron frame so that it cannot contract as it cools, 
it will rupture or pull itself apart, and then each part will 



contract. The same holds true of a casting. If a casting 
is made in the foundry without due regard to the contrac- 
tion stresses, it may come out of the mold broken. Some 
parts will have contracted more than others, and not being 
able to contract freely, naturally they have pulled apart. 
Every molder and pattern-maker knows how necessary it is 
to provide for contraction stresses in making castings. The 
success of the heavy iron founder largely depends on adapt- 
ing his work to the peculiarities of cast iron in this respect. 

Expansion is Proportional to the Rise in Temperature 

The expansion in length, breadth and thickness is pro- 
portional to the rise in temperature, and contraction is also 
proportional to the fall in temperature in the same ratio. The 
expansion rates of metals differ, being greater for copper and 
aluminum, for example, than for cast iron. The expansion of 
copper is about one-tenth of an inch per 1000 degrees F. per 
foot. This means that a copper bar one foot long expands 
one-tenth of an inch when raised 1000 degrees in temperature. 
A gray iron casting when preheated to 1500 degrees expands 
a little over one-tenth of an inch per foot, the expansion rate 
being 0.068 inch per foot 1000 degrees rise in temperature. 
Aluminum expansion is over twice that of cast iron ; the ex- 
pansion per foot per 1000 degrees is 0.148 inch. 

Great care must be taken when preheating aluminum cast- 
ings that the safe temperature is not exceeded. It is not safe 
to preheat aluminum over 600 to 800 degrees, and when 
heated the aluminum casting must be handled with great 
care as it becomes weak and brittle. 

Expansion Must be Provided for in Welding 

When we undertake to weld two pieces of metal together, 
we must provide for expansion, or we shall not be success- 
ful. The flame of the torch raises the temperature enorm- 
ously at the place where the weld is being made, and the 
heat spreads throughout the pieces. The welding is pro- 
gressive and as the metal is welded at a given point, the 
torch moves on and the metal begins to cool off and contract. 



The force of contraction may be so great that the joint will 
pull apart in places after it is welded. 

When preparing to weld two bars of steel together, we 
must lay them so that expansion and contraction will be 
provided for. The rule is to provide 2^ per cent of the length 
of the weld for expansion and contraction. If the joint is 10 
inches long we should lay the pieces so that the far end of 
the weld will be % inch further apart than the end at which 
welding is begun. If this rule is followed you will have little, 
or no trouble on a simple job. 

The action is this : The two pieces are laid with a space 
between them, which tapers so that it is %. inch greater at 
the far end. We tack them together and begin to weld. 
As welding proceeds, the molten metal cools and contracts. 
The contraction causes the parts welded to act like a hinge, 
drawing the unwelded ends closer and closer together as the 
welding proceeds. Finally, when the torch has reached the 
far end you will find that the ends have been pulled together 
to just about the right space for finishing the weld. If in- 
sufficient space is left contraction cannot take place in the 
cooling parts and destructive stresses may be set up. 

It is often an extremely difficult matter to provide for 
expansion and contraction when welding castings. In fact, 
the skill of the welder is displayed by the way in which he 
prepares the job and provides for expansion and contraction 
stresses. 

Effect of Torch Flame Comparable to Wedge 

The efifect of the torch flame on a casting may be com- 
pared to that of a wedge or tapered drift if driven into the 
crack or between the parts to be welded together. Suppose 
that a casting has a crack running from one edge toward 
the center. The place to start welding is the inner end of the 
crack. If the crack is short no preheating may be necessary 
because the stresses produced will be comparatively slight. 
But if the crack is long the local expansive effect of the torch 
flame may be disastrous unless it is reduced by preheating. 
You can see what the probable effect would be on a thin 



casting, say two feet square and having a crack in one side 
running toward the center a distance of six inches, if you 
drove a thin wedge into the crack. The effect would in- 
variably be to extend the crack and make the conditions 
worse. 

Suppose that the same casting has a blowhole near the 
center which you wish to weld up. If you start to weld in 
the hole you heat the metal to a high temperature around 
the hole and' produce expansion stresses of great force. The 
condition is practically the same as though you drove a tapered 
drift into the blowhole with a heavy sledge. The drift forces 
the metal apart to such an extent that the elastic limit of the 
iron is exceeded and a rupture results. So it may be when 
welding cast iron without preheating. 

"All that goes up must come down," and all that is ex- 
panded by heat above normal, must sometime contract to 
normal dimensions when the temperature returns to normal. 
Often the inexperienced welder has the unhappy experience 
of making a good weld in a casting and then seeing the 
metal crack elsewhere as it cools. He mends in one place 
and breaks it another. This is clearly due to contraction 
stresses resulting from not preheating or preheating at the 
wrong place. Preheating may be done so badly that it makes 
conditions worse instead of better. 

In the talk on heat and temperature we endeavored to 
make clear the difference between the heat of a body and 
the temperature of a body. Heat is expressed in quantity and 
temperature in degrees of intensity. The oxy-acetylene torch 
produces a flame of great intensity but of not much volume. 
It is true that we can change the amount of gas consumed, 
the size of flame and the amount of heat by changing the 
tips. But even with a large tip, the total amount of heat 
produced is not great compared with that which can be 
produced in a comparatively small furnace. 

Cost of Heat Produced by Torch too High for 
Preheating Use 

The cost of the heat produced by the oxy-acetylene torch 



is much higher than the cost of heat generated in a forge 
or with an oil blowtorch. You should get this very clearly 
in mind, as it has an important bearing on oxy-acetylene 
welding in general. The oxy-acetylene torch produces a flame 
of high temperature, but it yields comparatively little heat. 
The heat produced is more costly than the heat of a coal 
fire, charcoal furnace or an oil blast. 

In what has just been said about expansion and con- 
traction you learned something about the forces produced 
by heating and cooling and the necessity of providing for their 
free play. You cannot prevent a piece of metal expanding 
when it is heated, nor can you keep it from contracting as 
it cools. If you attempt to prevent expansion or contraction 
you are likely to cause a fracture in the welded joint or some 
other place. 




FIG. 1. HAUCK KEROSENE BLOWTORCH FOR PREHEATING 
CASTINGS AND FORGING FOR WELDING 

Preheating Necessary for Castings 

When welding a large casting or any casting of other 
than simple form, or even castings of simple form under 
most conditions preheating will be necessary. By preheating 



we mean heating the part to be welded with some other 
source of heat than the oxy-acetylene torch. The black- 
smith's forge fire may be used when the parts are compara- 
tively small but in general it is better to use some source 
of heat that can be readily applied to the parts when lined 
up on the welding table or to provide a special preheating 
fire or furnace on which the parts can be lined up and welded 
without moving after having been heated to the required 
temperature to relieve the expansion and contraction stresses. 
The choice of source of heat depends on local conditions 
and character of the work. An oil blowtorch or several oil 




FIG. 2. PREHEATING A BROKEN PULLEY SECTION WITH A FIRE- 
BRICK OVEN AND KEROSENE BLOWTORCHES 

blowtorches may generally be used with satisfaction if the 
castings are not too large. These torches are made in a 
variety of styles and capacities. They are simple, compact 
and produce a large soft flame of great heating power. One 
or more of these torches will soon heat castings to the 
degree where the broken parts may be welded without 
fear of setting up destructive expansion and contraction 
stresses. In localities where hardwood charcoal c^n be ob- 



8 



tained it is used in preference to oil blowtorches by some 
welders, however, as they believe better results can be ob- 
tained especially with large castings into which the heat has 
to be soaked for a long time before the internal stresses can 
be equalized. Another advantage of a hardwood charcoal pre- 
heating fire is that heat can be applied to the casting while 
welding is going on without creating highly uncomfortable 
conditions for the welder. The blowtorch flame, is likely to 
make things very uncomfortable for the welder if kept going 
after the welding starts. 

A preheating stove is a useful if not indespensable ac- 
cessory of the welding shop. It is satisfactory for preheat- 
ing comparatively light castings which may be laid on the 
top and heated by conduction and convection. The stove is 
operated with oil or gas and the flames do not come di- 
rectly in contact with the casting to be preheated. The pre- 
heating stove is not intended to be used as a welding table 
but merely for preheating parts which can be quickly welded 
after being removed to the welding table. 

Setting Up a Casting for Preheating and Welding 

When preparing a casting for preheating and welding it 
should be laid on the welding table, the preheating forge or 
a brick floor and blocked up with firebricks so that the flames 
from the blowtorch or charcoal may pass beneath. It is essential 
that the floor or table be fireproof, of course. In order that the 
blowtorch may be used economically it is desirable that the 
casting be so protected that the heat is not radiated rapidly. 
Asbestos paper is a convenient and efifective material for the 
purpose. It is furnished by the manufacturers in large sheets 
and is light, clean and easily applied. All parts of the casting 
should be covered except that part where the welding is 
to be done, and when the joint is welded it should be cov- 
ered also and the whole casting allowed to cool down uni- 
formly. 

If asbestos paper is not available, dry ashes or dry sand 
may be used to cover the casting and conserve the heat but 
such substances are not satisfactory for the purpose. It is 



difficult to apply dry ashes so as to cover all parts of a 
casting without using an excessive quantity. They are in 
the way when welding and are likely to fall into the joint 
and give trouble. When the job is finished there is a mess 
to clean up. By all means use asbestos paper if you can get 
it. The cost will be repaid many times in satisfaction, clean- 
liness and general efficiency. 

Preheating a Broken Pulley 

In the foregoing we have dealt with general preheating 
but often it occurs that preheating all over is unnecessary and 
even undesirable. If you have to weld a broken pulley you 
have a problem that requires some study. If a spoke is broken 
it could not be welded without providing for expansion and 
it is a difficult, expensive, and troublesome job to preheat 
a large pulley all over and, in this case, undesirable. What 
we should do in a case like this is to preheat the pulley rim 
and spokes each side of the broken spoke. The rim is ex- 
panded by preheating and the broken spoke pulled apart 
at the break. Now the oxy-acetylene flame can be applied and 
the break welded without fear of disastrous consequences. 

When the weld is finished it should be covered with 
asbestos paper and the heated parts of the rim may be ex- 
posed to the air. The problem is to make the rim and spoke 
cool down at such respective rates that there will be no severe 
contraction stress produced. A job like this requires some 
experience as a job welder but the theory is one that you 
can readily understand and apply as you are gaining experi- 
ence. 

If the pulley is broken in the rim, the hub should be pre- 
heated and a jack should be applied between the spokes so 
as to spring the broken rim apart. When the rim is sprung 
apart space is made available for welding and the conse- 
quent expansion. Here again experience is required in order 
to judge just how much the hub should be preheated and 
the rim sprung apart so that when welded and cooled it 
will be round and true. 

10 



Preheating a Bronze Valve Seat 

A bronze casting for an air pump valve chamber which 
forms a seat for several flap valves must be preheated for 
welding with due regard to the thin metal spiders that sup- 
port the guide for the valve stem in the center. If a casting 
of this type is preheated with a charcoal fire without proper 
protection for the thin metal sections the gases and flames 
will naturally pass through the openings and the thin metal 
parts will heat quickly to a high temperature long before the 
body of the casting has become hot. This is improper pre- 
heating. If a crack between adjacent valve seats is welded 
after preheating in this manner the probability is that the 
casting will pull apart in another place as it cools. The con- 
traction stresses set up are so severe that it would be a 
miracle if fresh cracks do not develop. A casting of this type 
must be handled intelligently. More skill is required for pre- 
heatitig than the actual welding. The flame of the preheat- 
ing fire must be prevented from passing through the openings 
and overheating the thin metal sections. This may be ac- 
complished by laying a thin metal plate over the fire and 
placing the casting on the plate. The flames then must pass 
around the plate and heat the casting indirectly. It will take 
longer to preheat in this manner but the results will un- 
doubtedly be much more satisfactorily in the long run. 

When a casting of this kind has a crack between two 
adjacent valve seats the aim in preheating should be to ex- 
pand the rim so as to separate the margins of the crack 
slightly. Then when welded the metal in the joint which 
has been raised to the fusing temperature will be able to con- 
tract without exerting a tremendous stress in the adjacent part. 
The rim will follow the contraction stress because it has it- 
self been expanded beyond the normal size. 

General Theory of Preheating 

The general theory of preheating may be expressed in a 
few words. Parts to be welded are preheated in order to 
overcome expansion and contraction stresses. It is cheaper 

H 



to heat a large metal casting with a charcoal, coal or oil 
fire than with the oxy-acetylene flame. Preheating must be 
done with reference to the individual job and no set rule 
can be laid down for preheating castings of irregular shapes. 
They should, in all cases, however, be preheated for the pur- 
pose of providing room for the local expansion produced by 
the oxy-acetylene flame and the amount of preheating should 
be calculated so that the parts will come back to approxi- 
mately their original position when cool. When large castings 
are preheated the radiating heat will be considerable no mat- 
ter how well they are protected. The welder should be suit- 
ably dressed for the job, and shields should be provided to 
fend off the radiated heat whenever possible. 

Effect of Preheating on Torch 

On very large and heavy work the use of special water- 
cooled torches will be necessary as the torch of the ordinary 
type may become so hot as to be unmanageable because of 
flashbacks. However, the skilful use of asbestos paper on a 
preheated casting will largely overcome the trouble many 
times. Another resort is a pail of water into which the torch 
is dipped from time to time to cool ofif the head. 

Questions 

1. In how many forms does matter exist? 

2. What is the effect of changes in temperature on 
dimensions of a casting? 

3. Why is it necessary to provide for changes of dimen-, 
sion due to changes in temperature? 

4. Why not use the torch for preheating castings? 

5. What is the advantage of the oil blowtorch for pre- 
heating? 

6. Why is hard wood charcoal preferred by some 
welders ? 

7. What should be done to conserve the heat when 
preheating? 

8. What precaution should be taken with a welded 
casting when cooling down? 

12 



9. How would you proceed to preheat a pulley with 
a broken rim? 

10. What would you do if a spoke only was broken? 

11. Having welded a broken pulley rim, how would you 
protect it while cooling down? 

12. How should the parts of a pulley be protected when 
the spoke only has been welded? 

13. What effect may preheating have on the torch? 

14. What should be done to stop the trouble? 



13 



Notes 



14 



Notes 



15 



DAVIS-BOURNONVILLE 

OXY«ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



PREPARING THE JOINT FOR 
WELDING 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonvilx-e Company 



PREPARING THE JOINT FOR WELDING 

Reason Why Beveling is Necessary — Angle of Bevel — ^Thick Casting Should 
be Beveled on Both Sides when Possible — No Beveling Required on Thin Alumi- 
num Castings — Methods of Cutting Bevels — Care Must be Taken to Remove All 
the Slag and Oxide from the Joint Before Starting to Weld — ^Parts Should be 
Cleaned — Alignment and Allowance for Contraction. 

One of the first principles of sound welding, as has been 
repeatedly stated in these lectures, is securing complete fusion 
and perfect union of the welding material and the edges of 
the plates to be welded. When the material is thin — say -^ 
to }i of an inch — you can weld successfully when the edges 
are square or as left by the cutting shear. The heat of the 
oxy-acetylene flame will penetrate deep enough to produce 
complete' fusion and satisfactory union. But when thicker 
plates are to be welded it is necessary to bevel the edges 
in order to obtain the best results. By beveling we; mean 
cutting away the corners so that when the two plates are 
brought close together they form a trough or vee. 

Reason Why Beveling is Necessary 

The reason for beveling the plates to be welded is easy 
to understand. It is necessary because the heat of the flame 
suitable for welding will not penetrate and produce perfect 
fusion beyond a depth of say ^ to -^^ inch. The depth of 
penetration, of course, depends on the size and shape of the 
flame ; the neutral flames that can be obtained with the smaller 
sizes of tips will not give much greater penetration than the 
depth stated. Hence, when the parts to be welded are thicker 
than % of an inch, we should cut away the metal at the 
sides in order that the flame may be free to operate on the 
center of the joint and fuse it perfectly clear through. We 
then fill in the vee by using adding material until it is level 
full. 

Angle of Bevel 

It has been found by experience that the sides of steel 
and cast iron plates should be beveled at an angle of about 



45 degrees. When two plates which are beveled at an angle 
of 45 degrees are butted together the included angle is double 
or 90 degrees. A lesser angle may be used on brass and 
bronze, and is generally advisable but the welder should not 
experiment with any but the recommended bevels until he 
has become skilled in the use of the torch and able to recog- 
nize instictively when he is getting perfect fusion and union. 
Then he can try welding plates with lesser angles of bevels 
until he finds just what the limits are. It is, of course, 
advantageous to use a lesser angle wherever possible as the 
amount of adding material and gas required are reduced. 

Thick Castings Should Be Beveled on Both Sides 
When Possible 

If the part is very thick and it can be approached' and 
welded on both sides, it is better to bevel and weld on both 
sides. The cross section area of the two vees when made 
of the standard angle is only one-half the cross section area 
of the single vee of the standard angle made all from one 
side. This you can readily prove for yourself by laying out 
a vee say for a two-inch plate, and then laying out two vees 
opposite in the same thickness of plate. 

The double vee reduces the amount of adding material 
and the quantity of gases required to weld. Moreover, you 
will obtain a better weld and less labor will be required for 
beveling the joint also. In many cases, however, it will be 
impossible to work on both sides of the piece. In that case, 
of course, the beveling must be done on one side only. Should 
the piece be very thick it is then advisable to reduce the 
included angle considerably ; if the angle is reduced to say 
60 degres for a thick weld, the skilled workman should be 
able to produce good work because he can so manipulate the 
torch that the actual welding will take place in an angle of 
approximately 90 degrees while the untouched sides of the 
trough will be at a lesser angle. In other words, if the sides 
of the vee are inclined at 60 degrees the skilled workman 
will start to work at the bottom and fill in so that the sides 
of the zone of welding are at a 90-degree angle and he will 



maintain this relation throughout until the job is finished. It 




fig; 6 COMPARISON OF PREPARATION 




FIG. 7 FOR VERY HEAVY SECTIONS 



Copyright 1919, by 
Davii-Boumonville Co, 



Davis Bournonville Institute 



SHOWING METHODS OF PREPARING THIN AND THICK METAL 
FOR WELDING 



would not pay, of course, to resort to this expedient on thin 
sections but on thick sections it will save much time, labor, 
adding material and gas. . 

No Beveling Required on Thin Aluminum Castings 

Cast iron and steel, as already stated, should be beveled 
at an angle of 45 degrees on each edge, making the included 
angle about 90 degrees. Aluminum need not be beveled so 
much as the lesser angle will work satisfactorily in most 
cases. In fact, when welding aluminum ^ inch thick or 
less no beveling at all is necessary where the welding iron or 
spud is employed to break up the oxide. Experience is re- 
quired, however, to work successfully in this manner as the 
operator must produce the weld without actually seeing it. 
He manipulates the molten metal with the welding tool work- 
ing out the oxide with a puddling hook so that the pure metal 
can flow together and produce intimate union. 

Methods of Cutting Bevels 

Various methods may be employed for cutting the bevel 
depending on the tool available. The quickest and easiest method 
generally to follow in the work shop is to grind the edges with 
an emery wheel using an ordinary floor grinder for the pur- 
pose when the parts are not too heavy. In the case of heavier 
castings which cannot be taken to the wheel, it is good prac- 
tice to use a portable grinder driven by a flexible shaft or 
an electric motor. In some welding shops swinging frame 
grinders are provided for beveling joints but they take up 
considerable room and are not as convenient to use as the 
flexible shaft arrangement. 

In the absence of means for grinding a bevel the work- 
man must cut away the metal with a hammer and chisel or 
with a file. Filing is a very slow and expensive process and 
the welder should learn to use the hammer and chisel ef- 
fectively. Chipping with a hammer and chisel requires con- 
siderable training but like most other operations, requiring 
manual skill, it is largely a matter of practice provided one 
starts out with the right kind of tools and follows approved 



methods. The choosing of hammer is important. Use a ball 
pene machinist's hammer weighing about 1^ pounds. The 
handle should be smooth and flexible. The length of the ham- 
mer over all should be about 16 inches. This is the hammer 
that will be used for most ordinary use but heavier and lighter 
hammers should be used for heavy and light work. A supply 
of sharp chisels should be provided. It is useless to try to 
chip a bevel on cast iron or steel without a sharp chisel. You 
cannot do it effectively any more than a carpenter can plane 
a board smooth with a dull plane. 

Hold the chisel easily in the left hand and grasp the ham- 
mer handle at the end and swing the hammer freely over the 
shoulder. Do not look at the end of the chisel but look at 
the point where you are cutting the chip. Of course, you will 
hit your hands some nasty raps when learning but you will 
make more rapid progress if you start right and stick to right 
principles. The workman who tries to chip holding the chisel 
in a death grip and hammer handle in the middle while he 
looks at the end of the chisel, is making hard work of an 
easy job. He works in anything but a workmanlike manner. 

The hammer and chisel when properly used are very 
effective tools, and we hardly over estimate the importance 
of learning to use them effectively. When chipping steel the 
chisel point will move more smoothly if it is dipped oc- 
casionally in oil. A small bunch of cotton waste saturated with 
oil may be laid alongside the work to lubricate the chisel edge. 

The hacksaw may be advantageously used for beveling 
castings, especially when light and easily broken. Successive 
cuts should be made with the saw along the margins, at an 
angle of 45 degrees. These cuts should be not more than ^ 
inch apart in ^ inch metal. When the saw cuts are finished 
the metal is cut away with the hammer and chisel. The saw 
cuts make chipping much quicker and easier, and reduce the 
chances of breakage. 

If a drilling machine is available, a series of circular vees 
can be drilled along the crack with a flat drill ground on 
the point to an angle of 90 degrees. The vees should be 
drilled until the point of the drill nearly penetrates the cast- 



ing. The hammer and chisel can then be used to cut away 
the partitions between the drilled vees very quickly. The 
vees should be drilled as close together or should even over-lap 
in order to leave as little metal as possible to be cut away with 
the chisel. 

If preparing steel parts for welding and much beveling 
is necessary it can be done much more quickly with a cutting* 
torch, however. The torch will remove ten cubic inches while 
one is being cut away by an emery grinder or a hammer and 
chisel. The welder should take advantage of all possibilities 
of his trade to save time and labor. Care must be taken 
to remove all the slag and oxide from the joint before start- 
ing to weld. 

When beveling the joint it is advisable in many cases 
to leave narrow parts unbeveled to assist in lining up when 
ready for welding. These narrow unbeveled parts are "wit- 
ness points" by which the original relation of the pieces can 
be ascertained and maintained. The location of these un- 
beveled parts will depend on the nature of the piece and 
its size. It should, in general, be as narrow as possible in 
order not to make broad defective spaces in the weld. It may 
be advisable in some cases to chisel them away after the 
casting has been tacked together and partially welded. 

Parts Should Be Clean 

When preparing parts for welding that are covered with 
oil or grease, it is generally advisable to clean them thor- 
oughly, using gasoline or kerosene to cut the grime loose. 
This may seem like unnecessary labor but it is not so. The 
workman cannot do the job justice if he is smeared with 
dirty oil and is in a generally uncomfortable condition. A 
little time spent in making the work clean and placing it in a 
position where he can work comfortably will be well spent. 
Cleaning the work will not only permit better welding to be 
done but it will save accumulating an unnecessary amount of 
grime and making the welder present a disreputable appear- 
ance. A skilled workman should be able to work without 
getting grease and dirt all over him unless it be on some 
emergency job where he is surrounded by unclean parts. 



Alignment and Allowance for Contraction 

Preparing the joint for welding includes alignment. When 
working in the workshop the alignment will be simplified 
by the use of a welding table. But when welding in the 
field the workman may have to resort to various expedients 
in order to obtain a satisfactory job. The use of straight- 
edges, levels, plumb bobs and the eye may be necessary. 
Look the broken casting over and see how the parts should 
be when welded. Block them up so that when tested with 
a straightedge they are in line or if the straightedge can- 
not be used, measure from a level floor. Unless means are 
available for aligning the broken parts carefully, it may be 
very unsafe to go ahead and weld as the result is likely to 
be unsatisfactory. It may be necessary in some cases to 
place the broken parts in their original position and mark 
them in such a manner that they can be aligned on the weld- 
ing floor to agree with the position when assembled. 

Remember that allowance must be made for the effect 
of contraction when welding without preheating. A steel test 
bar should be adjusted out of line slightly so that it will be 
approximately straight when welded. The contraction on the 
side of the vee will be somewhat more than for the opposite 
side unless preheated. 

Questions 

1. How deep will the fusing heat of the smaller torch 
flames penetrate into metals when welding? 

2. Why is beveling necessary? 

3. What is the greatest thickness of steel than can be 
welded without beveling? 

4. What is a prepared joint? 

5. What is the recommended angle of bevel? 

6. What should be the included angle when two beveled 
edges of steel plates are butted together? 

7. Why should thick castings be beveled on both sides? 

8. What is the reason why gas and adding material are 
saved by beveling on both sides? 



9. Is it necessary to bevel an aluminum casting %. inch 
thick? 

10. How would you proceed to cut the bevels on a light 
casting? 

11. Of what use is the hacksaw in beveling? 

12. When can the cutting torch be used for beveling? 

13. What precaution should be taken in regard to slag 
and oxide on a joint beveled with the torch? 

14. What is the first thing to be done when preparing 
to weld a greasy casting? 

15. What is the straightedge used for when setting up 
for welding? 



10 



Notes 



11 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

WELDING RODS AND FLUXES 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Form 387 



Copyright 1919 by the 
Davis-Bournonvii,i<e Company 



WELDING RODS AND FLUXES 

How a Tinsmith Solders a Joint — Soldering Differs from Welding — ^Welding 
Rod or Adding Material Should be Low in Carbon — A Welded Joint is a Fused 
or Cast Joint — Care Should be Taken of Adding Material — -Never Use Commercial 
Wire for Welding Rod— Reason Why Malleable Iron Should Not be Welded— 
Function of Fluxes — Flux Should be Chosen for Kind of Welding. 

When a tinsmith solders a seam in a tin can he melts the 
solder with the soldering bit and applies the bit to the tin which 
quickly rises to the amalgamating temperature and unites with 
the solder. The solder flows into the joint if the metal is 
made chemically clean by the use of tinner's acid or other flux. 
Nothing is fused but the solder and this is melted with the solder- 
ing bit. 

Soldering Differs from Welding 

But in oxy-acetylene welding the conditions are quite differ- 
ent. Welding rod or adding material is used to fill the joint the 
same as when soldering but it must not be melted by the direct 
flame of the torch. To do otherwise is to invite trouble. The 
welder must produce a puddle of molten metal in the parts to 
be welded which is sufficiently hot to melt the adding material. 
Then only can he be sure of perfect fusion and intimate union. 
The heat must be transferred from the torch flame through the 
puddle to the welding rod. The adding material then forms 
a dependable link between the sides of the joint, provided it is 
of the right material. The choice of adding material is very 
important. It must fuse without oxidizing easily and must have 
strength when cold in proportion to the strength of the parts 
welded. Success or failure may depend on whether or not the 
proper adding materials are used on the joint. Many failures 
of oxy-acetylene welding have been due to the use of fence 
wire or other commercial wire, in ignorance of the danger thus in- 
vited. 



Welding Rod or Adding Material Should be Low 

in Carbon 

Mild steel should be welded with a welding wire that is 
low in carbon content. The nearer the welding rod approaches 
in composition to pure Swedish iron the better will be the welded 
joint in general. Swedish iron melts under the neutral flame with 
very little tendency to oxidize, and combines with the molten 
steel smoothly, forming a union free from blowholes and hard 
spots. Some welders take pride in the fact that they are not 
limited to the use of the recommended welding rods and boast 
that they can use almost any ordinary wire picked up from 
the scrap heap. It is true that some commercial low carbon 
steel wire can be used for oxy-acetylene welding but it is not 
true that this nondescript wire will produce uniformly good 
weld's. The welders who use it deceive themselves and their 
customers. Sound welds cannot be made with commercial wire 
in general. Of course, it is true that many welding jobs require 
no great strength and a welded joint may be made strong enough 
with inferior materials to withstand all the stresses and shocks 
that it will ever be subjected to in use. The practice is so bad, 
however, that welders should not be backward in discouraging 
it wherever met. 

Why is the use of commercial steel wire bad practice? To 
answer the question we rrust go somewhat into the theory of 
welding and the influence of carbon on melting points. 

Why Swedish Iron or Special Low Carbon 
Steel is the Best Adding Material 

The reason why pure Swedish iron and special low carbon 
steel wire are better welding materials than ordinary commer- 
cial wire is first, the comparatively high melting point. The 
lower the carbon content of iron the higher its melting point. 
Pure iron melts at about 2,780 degree F. while the ordinary grades 
of mild carbon steel melt at from 2,500 to 2,600 degrees F. 
The temperature of the molten puddle of steel then must be 
raised nearly 200 degrees above the fusing point of the parent 
metal before the welding rod will be raised to the temperature 



i 



sufficient to cause it to fuse and add metal to the puddle. There 
can be Httle doubt when welding under this condition that the 
parent metal, puddle and adding material are perfectly blended 
when the joint cools off. Now you begin to see how important 
it is that the recommended practice of making the puddle melt 




0000 000 00 



3 4, 



a^^ ^-^ •^ 1^ |«^ rn r^ n n n n r 

'^ — ^ L-.-^' L-®' L^w L^ L^ l_^ L* LJ U U ^ 



5 6 7 8 9 10 11 ,12 13 14 15 16 



Davis Bournonville Institute 



FIG. 1. COMMERCIAL STEEL WELDING RODS AND GAUGE SIZES 

5 



the welding rod is when you compare the fusion temperature 
of various grades of steel and iron. 

What Happens when Commercial Steel Wire 
is Used for Adding Material 

Suppose the welder picks up from the scrap heap a coil 
of steel wire, having for example, a carbon content of from 0.25 
to 0.30. The carbon content may not be so high but he has 
no means of knowing what it is. Steel containing 0.30 carbon 
will melt at about 2,500 degrees F. or at a slightly lower tem- 
perature than mild steel plate of 0.10 carbon. Suppose the welder 
follows the recommended practice. He forms a puddle with 
the torch flame and applies his scrap adding material to the 
puddle. It melts readily and supplies the puddle. He welds the 
joint and regards the finished job with satisfaction! Suppose 
now the joint is put to a tensile test, and is pulled apart in a 
testing machine. What will be the probable result? The prob- 
able result is that that welded joint which looks so nice and 
smooth will pull apart under a stress of only 50 to 60 per 
cent of the strength of the unwelded steel plate. An examina- 
tion of the joint will show that there is a general lack of pene- 
tration. Tlie welding material adheres to the parent metal in 
spots. There is no general cohesion. It is more of a cemented 
joint than a welded joint. Why is this condition found? Because 
sufficient temperature was not produced in the puddle to insure 
breaking down the sides of the parent metal and complete union. 
The adding material melted at too low a temperature to form 
a sound weld. It is only by using the welding rods supplied 
by reputable manufacturers that you can be sure of the carbon 
content and the approximate fusing temperature of the metal. 
Do not get into the habit of using inferior materials as you 
will have reason to regret it some day when one of your jobs 
fails and seriously damages your reputation as a welder. 

A Welded Joint is a Fused or Cast Joint 

An oxy-acetylene welded joint is one united by fused or 
cast materials. You know that all cast materials are inferior 
in strength to rolled or hammered metals. But some cast ma- 



terials are better than others. You have seen cast iron so brittle 
and frail that it would break apart from a light blow with a 
hammer. On the other hand, you have seen some castings so 
strong that a comparatively light section could be broken only 
by a heavy blow with a sledge. So it is with an oxy-acetylene 
welded joint. If you use an inferior adding material you will 
make a cast joint of inferior strength. It may be so brittle that 
a light shock will break the joint apart and make your hours 
of labor useless. It is better to expend a few cents for adding 
material of known reputation than to run the risk of making 




FIG. 2. SIZES OF WELDING RODS, TORCH FLAMES, TIPS, THICKNESS 
OF METAL AND PREPARATION 



poor welds and saving a little money — when you risk so much 
by so doing. 

It is especially important when welding cast iron tO' use 
cast iron welding rods high in silicon. The analysis of a weld- 
ing rod, however, does not necessarily determine its value for 
welding. Much depends on the method of manufacture. Cast 
iron welding rods must not only be made from a fine grade 
of cast iron high in silicon and low in manganese and sulphur. 



but they should be made according to a certain approved method. 
Cast iron structure is affected by the rate of cooHng. The best 
cast iron welding rods are cast in metal molds which insure 
density of metal and freedom from blowholes and sand. 

Care Should Be Taken of Welding Rods 

You may not have realized this important fact that your 
welding rods should be clean. Never use a rusty rod or one 
covered with sand or dirt. A rod cast in sand is likely to 
have some sand adhering to its surface. The sand may melt 
with the iron and change the chemical make-up of the metal 
in the joint. The same holds true if your welding rods are 
rusty. Rust is oxide-of-iron. The oxygen in the rust may re- 
main in the molten metal and tend to make a weak oxidized 
joint. You know how careful you must be to adjust your gas 
to produce a neutral flame, you do this to avoid oxidizing the 
metal and take good care that you get the correct mixture. Then 
why be careless in the selection of your welding rods and thus 
defeat your care in adjusting the flame? If you are careless in 
the selection and care of rod you make practically useless all 
the care taken in flame adjustment and torch manipulation. 

Manufactured Welding Supplies 

The welding materials furnished by reputable concerns are 
carefully manufactured. They are put up in packages that pro- 
tect them from rust, and are cut in lengths convenient for use 
so that waste may be reduced to a minimum. This brings up a 
point in welding practice that should be observed carefully. The 
welder need waste no adding material as • he can readily weld 
a s'hort piece onto a longer one and thus use it up completely. 
He also should learn to bend steel and bronze welding rods 
to a convenient angle for use as a bent rod, whic'h can be applied 
with greater facility than a straight rod. Of course, cast iron 
rod's cannot be readily bent, and it is not common practice to 
use any other than straight lengths of cast iron stick. There 
may be conditions, however, that make the use of other than 
straight lengths desirable or necessary. Short sections of cast 
iron adding material can, of course, be welded to a long rod 
at an angle and used in this shape the same as steel or bronze. 

8 



How Welding Rods are Supplied 

Welding rods are commonly supplied for wrought iron and 
steel in various diameters ranging from -^^ inch to }i inch, in- 
clusive and in lengths of 36 inches. A 36-inc'h length makes 
two 18-inch lengths which are more convenient for use on many 
jobs. The accompanying illustration, Fig. 1 shows other sizes 
of welding wire by U. S. wire gauge number and the actual 
size. Fig. 2. shows the recommended size of wire based on 
Davis- Bournonville practice for welding steel up to and in- 
cluding 1 inch thickness. 

The diameter of wire should be chosen with reference to 
the thickness of the joint and the size of the tip and the flame. 
A small wire is not suited to the welding of a heavy plate. In 
the first place an excessive length is required to fill the vee 
and in the second place the small diameter wire exposes a larger 
surface proportionally to the oxidizing influence of the flame 
than a large one. The diameter of the wire should be as large 
as the puddle will melt freely. If too large a wire is used the 
heat abstracted from the puddle will tend to freeze it and dif- 
ficulty will be had in maintaining it in the proper state of fluidity. 
Hence, a welder must always choose the welding rod for a 
given job strictly with reference to the thickness of the plate 
and the size of the vee. 

Cast iron welding sticks are furnished in y^^, ^, ^ and yi 
inch diameters, and aluminum welding sticks — the cast metal — 
are furnished in 12-inch lengths, y\ to /i and -^j- inch diameters. 
The cast rods or sticks are used' on cast aluminum particularly, 
while the drawn rods or wire are preferable for welding rolled 
aluminum sheets such as are used in the manufacture of tea- 
kettles and other kitchen utensiles. 

Brass and bronze are welded with cast welding sticks and 
drawn bronze rods. These are furnished in a variety of diame- 
ters and length. Brazing wire in the smaller diameters is 
furnished in coils while the larger diameters are furnished in 
36-inch lengths. The same applies to wire for copper welding. 
Brass wire is not a suitable adding material for welding as it 
contains a large percentage of zinc. This burns out at a com- 
paratively low temperature, making dense white fumes. The 



fumes are poisonous to the operator, and the welding material 
is defective in strength when the zinc has been burned out. 
Bronze rods produce a much stronger joint and are less harm- 
ful to the operator. 

Malleable Cast Iron should be Brazed 

Malleable cast iron is a white cast iron which has been 
subjected to an annealing process that converts the outside shell 
to a grade of iron having some of the characteristics of wrought 
iron ; a malleable casting will bend before it breaks. Malle- 
able iron is used where ordinary gray iron castings are not safe 
on account of heavy loads, and shock. It is not good practice 
to weld malleable iron parts because the joint produced will be 
one of cast iron. Even if steel adding material is employed the 
joint will necessarily be weak because the fused edges of the 
casting are changed from malleable iron to a poor grade of cast 
iron when held under the torch. Hence, a welded malleable 
casting is likely to be unsatisfactory. In the first place, you 
have a casting made of malleable iron because the situation re- 
quires greater strength than can be gotten in a gray iron casting 
and in the second place, the malleable casting having broken, 
shows that the stresses are too great even for the malleable 
part. It is, therefore, useless to restore the broken casting with 
a welded joint inferior in strength to the original structure. 

When the welder is confronted with a broken malleable part 
he should recognize the metal and proceed accordingly. The best 
practice is to braze the joint with bronze welding wire and an 
approved brazing flux. A properly brazed joint in malleable cast 
iron will be as strong as the original section of malleable iron. 
It is not necessary when brazing to raise the metal to the melt- 
ing point. Hence, the malleable characteristics of the iron are 
left unchanged. 

Function of Fluxes 

When a tinner solders a joint he uses rosin or acid to make 
the solder flow smoothly. If solder is dropped' on an un- 
clean metal surface it will remain in isolated drops and refuse to 
amalgamate with the metal beneath. The reason for this is 

10 



the thin film of oxide which prevents intimate contact. The 
tinner's acid dissolves the oxide and permits the molten solder to 
unite with the surface beneath and cover it smoothly. The rosin 
acts as a protective, preventing the formation of oxide and facili- 
tating the flow of solder. Metals in the molten state have a strong 
affinity for oxygen, as is shown by the oxide film or dross that 
quickly forms on the surface. If the surface of molten metal 
is covered with some substance that protects it from air, oxidiza- 
tion will be greatly reduced or eliminated entirely. Hence, in 
welding materials that are easily oxidized it is advisable to use 
a scaling powder or flux which protects the metal and makes 
the union of the fused metal easy. 

The function of flux in general, therefore, is to prevent 
the formation of oxides and to eliminate oxides already formed 
and to act as a solvent or loosener of trapped oxide and slag. 
Cast iron for example, has a strong attraction for oxygen when 
molten and the use of a scaling powder or flux will be found 
necessary. Cast iron melts at a lower temperature than iron 
oxide and unless the oxide is dissolved it will be found impos- 
sible to produce a sound weld. The metal will stand in drops 
and act much the same as solder on an unclean tin surface. The 
addition of a little scaling powder acts like magic causing the 
drops to coalesce and unite with the parent metal. 

Some of the troubles caused by the presence of oxide are 
eliminated by increasing the heat sufficient to melt the oxide 
film. Steel and wrought iron when melted tend to form oxide 
the same as cast iron but the higher melting temperature re- 
quired melts the oxide and so it gives little or no trouble. 
However, flux is not amiss on steel sometimes, especially if the 
carbon content is rather high, and a first-class smooth job is re- 
quired. 



Composition of Fluxes 



The blacksmith from time immemorial has used common 
river sand or silica when welding wrought iron. The silica melts 
and forms a coating of molten glass which acts as a protection 
for the white hot iron and prevents it being oxidized by the 
blast. Protected by this coating the iron may be safely raised 

11 



to the welding temperature without burning. It must be knocked 
off when the iron is ready for welding and this is accomphshed 
by giving the bars a smart blow upon the anvil. 

There are many other materials that can be used for fluxes 
in welding the various metals and some welders compound their 
own fluxes, but in general the use of homemade fluxes is not 
wise. Powdered borax is commonly used for brazing brass, 
bronze and copper but unless calcined it gives much trouble 
by bubbling and frothing due to the contained water of crystal- 
lization. Preparations are available at somewhat higher cost, 
which work well and save time, trouble and annoyance. These 
are important factors in efficient welding. The work should 
be made as easy as possible and false economies should be 
avoided. Many a penny is saved at the spigot while dollars 
are lost at the bunghole in the welding shop. The chief 
items of expense are the gases and labor. Make labor efificient 
and save gas. A few cents saved in a s'hop compounding a flux 
may be lost many times over in the added cost of welding. 
Hence we do not advise the manager of a welding shop giving 
much attention to so-called cheap compounds for scaling and 
fluxing. "It is better to be sure than sorry." 

The proper preparation of a flux rec[uires careful propor- 
tioning of the material and intimate mixing with machines. 
The ingredients must be finely pulverized and intimately mixed 
in order to produce a flux that will be uniform in its action 
on the fused metal. An improperly mixed flux is uncertain 
in its effect as the chemical action on the metal will d'epend 
on the precise composition of the portion in contact on the 
instant. If it happens that a certain ingredient is in excess 
it might well produce an indefinite or detrimental action. Hence, 
the matter of mechanical preparation of the flux is often as 
important as the chemical make-up. The chemical action can- 
not be predicted unless it is known that the materials are thor- 
oughly incorporated and applied in uniform proportion, no 
matter whether a large or small amount is used. 

The use of fluxes is strictly necessary on many kinds of 
welding and the proper flux should always be provided but 
the oxy-acetylene welder should avoid placing too much reliance 
in fluxes and scaling powder, as cure-alls for welding troubles. 

12 



Proper flame adjustment and torch manipulation will avoid many 
of the troubles that unskilled welders attempt to overcome by 
the liberal use of fluxes. The envelope of the neutral flame is, in 
itself, a protection to the molten metal, and if the flame is properly 
adjusted and the joint is welded quickly without exposing the 
puddle to the oxidizing atmosphere, the need of flux will be 
reduced to a minimum. The skilled welder uses but little flux 
buit he uses it intelligently and chooses the right kind for the 
job in hand. 

Questions 

1. What is the function of a flux? 

2. What is a common flux used by blacksmiths? 

3. What is the efifect of carbon on the melting point of 
steel ? 

4. Why should a welding rod be low in carbon content? 

5. What is the character of a gas welded joint? 

6. Why should the welder avoid the use of rusty welding 
rods ? 

7. What is the difference between adhesion and cohesion? 

8. At about what temperature does Swedish iron fuse? 

9. Why is it bad practice to use commercial wire for adding 
material ? 

10. What is the probable result of using ordinary cast iron 
welding rods for cast iron welding? 

11. Why should malleable cast iron be brazed? 

12. What material should you use for brazing malleable 
iron ? 

13. It is necessary to use flux when welding mild steel? 
Why? 

14. Why is flux necessary when welding cast iron? 

15. Why is it poor economy to make your own flux? 



13 



Notes 



14 



Notes 



15 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDIING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

SHAPE OR MOLD WELDING 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 

DAVIS-B0URN0NVIl,t.E COMPANY 



SHAPE OR MOLD WELDING 

Use for Salvaging — Shape Welding — Mold or Dam Welding — Use of Car- 
bonite Rod — Replacing Broken Gear Teeth — Carbonile Molds — Restoring Worn 
Journals. 

What mechanic has not wished for a "putting-on tool" when 
he has turned a piece too small or has planed off too much by 
taking an injudicious depth of cut? The putting-on tool was a 
figment of the imagination and a practical joke until the oxy- 
acetylene torch came into use. It made the impossible not only 
possible but practicable. 

Use for Salvaging 

It is now a not uncommon practice to salvage parts that have 
been spoiled by improper machining or that have been reduced 
by wear. Worn journals can be restored to the original diameters 
by welding a thin layer of steel to the surface. Of course, the 
welded metal on the journal must be turned and polished in a 
lathe before it can be used. There are many other machine parts 
that can be made whole again by building on adding material and 
machining to the required dimensions and finish. One of the 
most frequent accidents to machinery is the breaking of gear 
teeth. A gear with a broken tooth is practically useless, and it 
may represent an investment of several hundred dollars. Ord- 
inary methods of patching in a new tooth are mostly worth- 
less as a patched tooth will have so little strength that it will 
be broken out as soon as an extra heavy load has to be trans- 
mitted. A tooth built up of adding material is as strong and 
durable as the original if properly done. 

One of the interesting and unusual applications of the oxy- 
acetylene torch in this line is depositing a coating of cast iron on 
the seats of steel poppet valves used in gas engines. Cast iron 
resists the heat and abrasive action of exhaust gases superior to 
steel. The cast iron forms a seat on the poppet valve equal to that 
in the cylinder casting, and outlasts several steel S2ats, thus reduc- 



ing the cost of upkeep. The cast iron coating of course must 
be accurately finished the same as the soHd steel valve but being 
much more durable the cost is well repaid. Steel plates that 
have been punched incorrectly may be restored at low cost when 
a few holes of small diameter are out of place. The welded 
sheet may then be correctly punched and used without fear that 
the restored parts will fail in use. This operation is not, of 
course, shape or mold welding but it comes under the general head 
of salvaging manufactured parts or making old boiler plates use- 
ful for new purposes. 

Shape Welding 

There are two distinct kinds of shape welding, one being ac- 
complished by torch manipulation alone and the other by the aid 
of dams and molds of high heat resisting material. A boss can 
be built upon the face of a gray iron casting of any size and 
height by fusing on adding material in the quantity required. It 
is not difficult for the experienced welder to keep the margins 
from sloughing off or to control the shape of contour to simple 
forms. It is done by graduating the heat so that the molten 
metal at the edges is near the freezing temperature and flows only 
when the flame is held close. The moment it becomes too fluid 
the flame is whipped off and directed upon a colder part. The 
Same manipulative skill is required as in finishing the end of a 
joint square. Less heat must be applied than in the center when 
finishing a joint and the torch is whipped up whenever the metal 
gives signs of breaking down and overflowing the edge. 

Bosses can be built not only vertically but horizontally and 
at any intermediate angle at will. The usefulness of boss weld- 
ing in repair work is obvious, and welders should practice it not 
only to acquire skill in forming bosses but to perfect themselves 
in the art of finishing welds square and in a workmanlike man- 
ner. 



Mold or Dam Welding 



When a new lug, ear or other part is required to replace one 
broken from a casting, it is generally advisable to make use of 
a mold or dam of some material like carbon blocks or carbonite 



which resists the heat of the torch flame and which can be readily 
cut, carved, sawed and drilled. Carbonite possesses these qualities 
in a most satisfactory degree, and is used generally for shape 
welding and also as a retaining wall for difficult side seam and 
vertical seam welding. 

Suppose a lug has been broken from a casting and lost. To 
replace it is a matter of merely providing a carbonite mold of the 
shape required, open at the top and placing it against the casting 
with the opening opposite the break; the block is weighted down 





Davis Bournonvllle Institute 



FIGS. 1 AND 3. USE OF CARBONITE ROD AND BLOCK FOR SHAPE 

WELDING 

and the welder proceeds to fuse the face of the casting and' sup- 
ply adding material until the mold is filled to the required height. 
If the lug was recovered it is often cheaper to build up a new 
one in a mold than to weld the old one in place. The preferable 
practice depends on the size and other conditions. 

Preheating the casting is advisable in order to prevent ex- 
cessive expansion and contraction stresses, and the lug and cast- 
ing should be covered with asbestos paper or other insulating 
material in order to prevent rapid cooling. 



Use of Carbonile Rod 

Carbonite is supplied in blocks or slabs, in various thick- 
nesses from ^8 inch to 1 inch, in width up to 6 inches and lengths 
o£ 36 inches. Rods of the same are furnished in diameters of ^ 
inch to 1 inc'h, inclusive. Carbonite rods are used to fill holes 
when welding radiating cracks. If properly placed the walls 
will maintain their shape and thus render boring or reaming un- 
necessary. It will burn away slightly so that a little filing only 
will be required. In fact the judicious use of carbonite rods will 
often make welding feasible that otherwise would be impractic- 
able on account of cost of subsequent machining. 

Replacing Broken Gear Teeth 

Broken gear teeth may be replaced successfully on all kinds 
of gray iron and steel gears but it is not advisable to attempt the 
replacement of the teeth of motor car transmission gears except 
as an emergency repair. These gears are generally made of alloy 
steel and specially heat-treated to give them toughness and dur- 
ability, and unless the welded teeth are made of the same metal 
and heat-treated the job will not last. However, there are many 
other broken gears that can be repaired with uniform satisfaction. 

The practice of replacing broken teeth depends on the gear 
and local conditions. A gray iron gear with cast teeth can be 
repaired by building up a new tooth alone, using carbonite blocks 
in the adjacent spaces to hold the new metal closely to the gen- 
eral thickness of the old tooth. Care must be taken in preheating 
not to crack the rim and the welded tooth must be protected from 
cooling down too rapidly when complete. When the welding is 
finished and the casting has cooled down the tooth is ground to 
shape with a portable emery grinder or chipped and filed to a 
templet. 

If the gear has cut teeth and a gear cutter of sufficient capac- 
ity is available the preferable practice is to build in the broken 
teeth and adjacent tooth spaces solid with new metal, and then 
cut two spaces on the gear cutter. This should produce a solid 
well formed tooth. An alternative method less expensive but not 
so likely to produce a good job is to build in the tooth with 



carbonite blocks alongside, and finish with the gear cutter. The 
difficulty is that the cutter is at disadvantage in cutting, having 
to cut metal on one side only. Springing and chattering are bound 
to result making considerable hand finishing necessary. 

Carbonite Molds 

In an emergency small castings may be made entirely with 
adding material and a mold formed of carbonite blocks and rods. 
In some cases adding material can be saved by using chunks 
of scrap cast iron to fill the larger spaces. The welding stick 
is then used to fill in and join the parts only. Of course, resort 




FIG. 3. RESTORING BROKEN GEAR TEETH WITH AND WITHOUT 
CARBONITE BLOCKS 

should never be made to this method except when the need of 
the part is so great that the cost is a secondary consideration. 

In conclusion let us impress the value of carbonite in the 
welding shop again. It is easily cut or carved to any shape re- 
quired and having high heat-resisting quality it can be used in 
welding with general satisfaction. It can be turned in the lathe, 
planed, drilled, cut with a hacksaw, carved with a knife, filed with 
a rasp and, in fact, can be easily shaped to any form required 
with ordinary tools. Being supplied in slabs of different thick- 



nesses and in rods of various diameters the welder can usually 
select the commercial size that most nearly meets his needs and 
thus save considerable unnecessary labor. When used for plugging 
a hole to support metal needed to replace a broken away section 
no allowance need be made in the carbonite for finishing. It will 
burn away sufficiently to provide enough excess metal in the 
hole for filing smooth and true with the remainder. Often it is 
used to protect threaded holes close to sections that must be 
welded. In that case the carbonite should be fitted as closely as 
possible. If it fits so closely that a thread is cut in it while 
screwing into place so much the better. 



Restoring Worn Journals 

When restoring a worn journal the shaft should be preheated 
and kept hot throughout the operation. It should be supported 
on vees so that it can be turned around as the building on pro- 
ceeds. The adding material should be laid in thin strips length- 
wise, taking care to secure penetration into the shaft and blend- 
ing with the strip already laid. If skillfully done the journal 
should not be sprung or distorted so much that an ordinary fin- 
ishing cut on the journals will not bring them true. But a re- 
stored shaft should be tested on centers for truth before starting 
to turn, and if it runs out it must be straightened first with a 
shaft straigfhtener. 

Questions 

1. Can you give a good example of the use of the oxy- 
acetylene torch as a "putting-on" tool ? 

2. What precaution must be taken when restoring worn 
shaft journals to the original diameter? 

3. How would you proceed to restore a broken tooth in a 
cast gear ? 

4. In what respect does the practice of restoring cut gear 
teeth differ from that followed on cast teeth? 

5. Which is the best practice to follow when restoring 
broken teeth in cut gears — building up one tooth alone, 
or building the tooth and filling the adjacent tooth 
spaces with adding material? Why? 



6. What do you understand by shape welding? 

7. How is it possible for a welder to build up a boss with 
a torch? 

8. Do you see in boss welding the same manipulative skill 
required to finish the end of a joint? 

9. Which is preferable when restoring a broken lug, to 
build up a new lug of adding material or weld on the 
old one? 

10. What material is recommended for a mold or dam when 
building on a lug or gear? 

11. Why is it necessary to use a material of high heat-re- 
sisting quality? 

12. What form of carbonite is useful when welding a 
rack running into a finished hole? 

13. How would you proceed to build up a worn journal? 

14. How would you proceed to protect a threaded hole 
when welding close by? 

15. Mention an example of building up with adding mate- 
rial to improve the wearing quality of a bearing or seat. 



Notes 



10 



Notes 



11 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

WELDING DISSIMILAR 
METALS 



OAVIS-BOURNONVILLE INSTITUTK 

JERSET CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonvi]:,i<e Company 



WELDING DISSIMILAR METALS 

Difference Between Autogenous Welding and Soldering — Metal of High 
Melting Temperature Should be Fused First — -Welding Steel and Copper — Welding 
Machinery Steel and Tool Steel — General Rule for Welding Dissimilar Metals. 

It is a remarkable fact that the oxy-acetylene torch can be 
used successfully for welding practically all metals. Cast iron, 
steel, wrought iron, aluminum, bronze, copper and many alloys 
can be welded effectively. Some metals weld easier than others, 
but practically all can be fused and soundly united by welders 
who know how to use the torch and' adding materials. Not only 
can all the commercial metals be welded, but combinations of dis- 
similar metals may also be welded satisfactorily ; it is a matter of 
daily practice to weld steel to cast iron and steel to copper. 

Difference Between Autogenous Welding 
and Soldering 

The fact that dissimilar metals also can be successfully 
welded is one of the differences between autogenous welding and 
soldering. Soldering in general must be practiced on similar 
metals or metals whose specific heat and amalgamating tempera- 
tures are nearly the same. Some metals, aluminum especially, 
cannot be soldered at all, or only with great difficulty. There 
are aluminum solders and workmen who can solder aluminum, 
but most aluminum soldered joints have a very disagreeable way 
of parting company after a few weeks. This action is ascribed 
to electrolysis in the joint which eventually disintegrates the 
solder and causes the separation. The most successful method 
of uniting aluminum is by autogenous welding, using the oxy- 
acetylene torch; the fused metal runs together, making one 
homogenous piece. 

Metal of High Melting Temperature Should Be 
Fused First 

In welding dissimilar metals it is necessary to manipulate 
the torch so that the metal of hig'hest fusing temperature is 



played on most. The adding material is built up on the metal 
of the lower fusing temperature, and then is united with the 
metal of hig'her fusing temperature. When the fusing tempera- 
ture of one metal is high and that of the other is low the job 
offers considerable difficulty and can be successfully accomp- 
lished only by one who has acquired considerable experience 
and skill in handling the torch. It is practically necessary under 
such conditions to maitain different zones of heat on the two 
sides of the joint, the highest zone, of course being on the side 
of the metal having the highest melting temperature. The add- 
ing material must be chosen with reference to this condition, and 
it must be used with skill in order to secure satisfactory re- 
sults. 

Welding Steel and Copper 

A not uncommon requirement is to weld copper bonds to 
street car steel rails. The copper bond's are only ^ to ^ inch 
thick and the steel rail has several times greater cross section. 
The melting or fusing temperature of steel is considerably higher 
than that of copper, and in order to make the job commercially 
practicable the welder must make a study of such welding, and 
apply his knowledge with his best ability. 

Welding is accomplished by first forming the molten puddle 
on the steel, and inserting the end of the copper bond and fusing 
it, while protected by an approved copper welding flux. Bronze 
wire is used for adding material, but little is needed as there 
should be no attempt made to improve the weld when the copper 
and steel have united over an area of contact equal to or greater 
than that of the bond cross section. Then is perfect conductivity 
assured, and that is the one and sole reason for welding the bonds 
to the rail. 

In passing, your attention is drawn to the fact that the only 
perfect electric joint is a soldered, brazed or welded joint. An 
electrical connection made by a mere contact is likley to offer 
high resistance to the current on account of the oxide film that 
quickly forms on the clean, bright surfaces of all commercial 
metals. These oxides offer high resistance, and may, in time, 
become so pronounced as to interrupt the flow of low voltage 
currents entirely. It is not an uncommon experience to find 



an electric light bulb, long unused, that refuses to light when 
the switch is turned on. But loosening the lamp and screwing 
it into the socket again breaks the oxide film and permits the 
current to flow through the lamp. Hence, it is obvious that 
autogenous welding of similar and dissimilar metals has a valu- 
able characteristic for electrical work, requiring permanent con- 
nections of high conductivity. The use of aluminum before the 
war for electrical connectors was becoming quite common, and be- 
cause of the difficulty of welding aluminum, the oxy-acetylene 
torch was the favorite means of producing the desired welded 
joints. 

A brass nipple screwed into a steel drum may give trouble by 
leaking under high pressure and for that reason require to be 
welded. Of course, the welder will avoid playing the torch flame 
on the nipple before he has raised the steel to the fusing heat. In 
fact, the fused steel will act the same as the puddle on the add- 
ing material stick ; it will melt the brass and unite with it readily 
especially if a little bronze welding flux is used. The welder 
should work quickly and as close to the nipple as possible making 
the weld complete as he goes along. Bronze welding wire should 
be used to fill the joint and form the fillet. The weld, if made at 
a low temperature, will have the characteristics of a brazed joint. 
For most situations this will answer. It has the advantage of not 
requiring a heat likely to injure the brass. 

Welding Machinery Steel and Tool Steel 

The influence of carbon in steel is to lower the fusing temper- 
ature, the greater the carbon content the lower the melting point 
within certain limits. Pure iron and mild steel require several 
hundred degrees higher temperature for welding than high carbon 
steel and high-speed steel. The danger then in welding tool steel 
and machinery steel is that the heat required to melt the machinery 
steel will burn the tool or oxidize it to a degree that renders it 
worthless. Hence, great care has to be taken to graduate the heat 
so that fusion without overheating is obtained. 

One of the jobs that welders employed in manufacturing 
shops may be required to do is welding high-speed steel tips to 
machine tool shanks to form metal cutting tools. The cost of high- 



speed steel is from $3.00 to $3.50 a pound or more. A large planer 
tool may easily weigh ten or twelve pounds, and inasmuch as only 
a few ounces of steel at the point do the cutting it is practically 
unnecessary that ten pounds or more of high-priced steel be used 
as a shank merely to support the cutting tool. A high-speed steel 
tip welded to a machine steel shank serves the purpose fully as 
well, and the investment in high-speed steel is reduced 80 or 90 
per cent. 

To weld a high-speed steel bit to a machine steel or carbon 
steel shank is not easy but it can be done and done well if certain 
rules are followed. The first step is to plane the machine steel 
shank across the end so as to form a notch or shelf on which the 
high-speed bit will be supported while under the pressure of the 
cut. The edges should be beveled to an angle of say 55 to 60 
degrees or more in order to avoid beveling the edges of the tool 
bit and wasting the high-priced steel. If the tool is large it is in- 
advisable to attempt to weld the entire surface of the bit to the 
shank ; it will suffice to weld the edges and depend on the support 
provided by the notch to carry the thrust on the joint. Preheat 
the parts and weld with a Swedish iron welding rod, or the 
adding material recommended by the manufacturers of oxy- 
acetylene apparatus for the purpose. The welder fuses the ma- 
chine steel first and "tins" the bit with the iron adding material 
before undertaking to weld it to the machine steel shank; w'hen 
the high-speed steel has been "tinned" with the iron adding ma- 
terial it is not then so difficult to unite the iron adding material 
to the steel shank. 

Extra length twist drills are sometimes required for drilling 
deep holes, and a machinery steel shank must be welded to a com- 
mercial twist drill of the desired size. The joint should be scarfed 
or beveled, making the length of the bevel two or three times the 
diameter of the drill. A half-round groove should be planed in 
a carbonite block in which the drill and' shank can be laid hori- 
zontally for welding. If of small diameter place the parts in the 
groove so that the bevel of the shank overlaps the drill, and pro- 
ceed to fuse the machinery steel working on the theory that the 
heat transmitted to the high-carbon steel beneath will be suffi- 
cient to fuse it and produce a weld. Use but little adding ma- 



.._-Jb... 



terial at the edges. But if the drill is one-half inch diameter 
or larger it will be necessary to tin it with adding material be- 
fore laying the shank in place and the edge of the bevel on 
the shank must be beveled in the usual manner to let the adding 
material enter and make a sound union. After welding, the ex- 
cess metal is ground ofif to the drill diameter. 

General Rules for Welding Dissimilar Metals 

In general, the rule for welding dissimilar metals is summed 
up in a few words, as follows : Fuse the metal of compara- 
tively low melting temperature and coat it with approved adding 
material ; then weld the coated or tinned part to the piece having 
the higher fusing temperature. ' Avoid directing the torch flame 
upon the metal of low melting point more than absolutely neces- 
sary to tin it and secure a union with the adding material. 

When care is taken to do a good job of coating and the 
adding material is chosen with reference to the characteristics 
of the two metals to be welded it is not out of the question to weld 
metals having quite widely different melting temperatures. Of 
course, there are practical limitations to w'hat can be accomp- 
lished in welding different metals, both on the score of cost and 
difference in expansion coefficients. It is obvious that long welds 
cannot be successfully made with two metals having widely dif- 
ferent rates of expansion and contraction. The internal stresses 
produced will bend the welded parts or pull the welds apart. But 
in welds of comparatively small area or length the stresses thus 
produced are small and negligible. Tack welding may sometimes 
be used' with satisfaction on long welds if not subjected after- 
wards to great temperature variations. Tack welds do not re- 
quire preheating and fusing throughout the length of the joint. 

Questions 

1. What metals can be welded with the torch? 

2. What is the rule regarding the use of adding material when 
welding on metal? 

3. Why is it generally difficult to weld dissimilar metals? 

4. In what respect does welding differ from soldering? 



5. When welding two dissimilar metal parts which one should 
be welded first? 

6. What is "tinning" when welding dissimilar metals? 

7. Which metal should be "tinned" w'hen welding? 

8. What is the effect of carbon on the melting point of steel? 

9. Which melts first, mild steel or high carbon steel? 

10. What is the danger when welding mild steel and high carbon 
steel ? 

11. How would you proceed to weld a high-speed steel bit to a 
machine steel shank? 

13. Is it advisable to attempt to make long welds between dis- 
similar metals? Why? 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

GAS WELDING MACHINES 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY. N. J. 



Form 390 



GAS WELDING MACHINES 

Hours of Practice Required to Master Hand Welding Torch — Welding Ma- 
chines Suited for Manufacturing — Gas Welding Machines — Machine Welding 
Torches — Clamping Work for Machine Welding — Special Welding Torches for 
Machine Use — Machine Welded Pipe Joints. 

Oxy-acetylene welding torch practice requires a high degree 
of manipulative skill of the welder; he must hold the torch 
with the tip of the white hot cone close to the work and always 
far enough away so as to prevent occlusion of gases, but not so 
far away that the maximum heat is not imparted to the metal 
just ahead of the puddle. He must always give the torch a 
continuous motion, either a straig'ht zig-zag or a semicircular 
zig-zag across the joint, advancing at the same time in the di- 
rection of welding as the puddle progresses. With the other 
hand he must hold the welding rod in a certain relation to 
the torch and work. When welding aluminum without flux he 
must frequently pick up the puddling hook, work out the oxide 
and all the time hold the torch in the proper position. 

Hours of Practice Required to Master Hand 
Welding Torch 

It is easy to show a learner how to hold a welding torch 
and manipulate it but to acquire the skill requires many hours 
of practice before one is able to follow the directions easily. No 
one can long work efficiently when under strain, and as it is 
necessary for the welder to learn to stand easily and operate 
the torch correctly without giving thought to anything except 
the puddle and the direction of the welds he must practice 
torch work daily for sometime before he becomes sufficiently 
proficient to be put on regular work. The welder who is 
really proficient picks up the welding torch and goes to work, 
exercising the same sub-conscious development that enables you 
to walk, dance, ride a bicycle or skate without balancing effort. 
Practice only will enable you to develop the master's skill, and 



it is essential that you learn the most efficient method at the 
start and thus avoid falling into bad practice. 

Welding Machines Suited for Manufacturing 

The hand welding torch and skilled operator must always 
be used for welding a large variety of s'hop and field repair 
and fabricating work. But it is not necessarily the only means 
available for welding duplicate parts made in quantities. Early 
in the development of the oxy-acetylene torch practice the pos- 
sibility of holding and guiding the torch mechanically was recog- 
nized and machines were devised for the purpose with a view 
of utiHzing the apparently great possibilities of the gas torch 
for manufacturing. A description of a machine for gas welding 
tanks and parts of boilers was published in France in 1907 and 
other machines for welding had been worked out sometime be- 
fore. 

It is obvious that when parts are to be manufactured in 
quantities that require welding it is easily within the bounds 
of possibility to design and build a welding machine to hold 
the torch in the proper relation and to feed either the work 
or the torch along at the required rate to produce a perfect 
weld in thin stock which requires no adding material. Gas weld- 
ing machines have been applied successfully in the manufacture 
of pipe, tubing, range boilers, steel barrels, battery boxes, elec- 
trolytic cells and similar products made in large quantities. The 
steel used is thin, generally not more than 3/32 inch thick and 
requires the use of no adding material. Hence, there is no com- 
plication in the machine due to holding and feeding welding rods 
to the joint. Doubtless, it would be possible to machine weld 
prepared joints and feed welding rod to the joint at the re- 
quired rate but so far as known this has not been commercially 
accomplished. In fact, the possibilities of machine welding have 
as yet been developed to a comparatively small degree. But it 
is apparent that special welding apparatus will produce machine 
welded parts cheaply that are practically impossible of com- 
mercial production by other methods. The rate of production is 
rapid and even if the parts can be hand welded the welding 
machines do the work so much faster that hand operation is 



generally out of the question. Moreover, a welding machine 
makes smooth, uniform welds without adding material. A 
peculiarity of welding machines is that adding material is not 
required where it would necessarily be used if hand welded. 

Gas Welding Machines 

Tube, pipe and boiler welding machines have been devel- 
oped abroad and in this country. The Davis-Bournonville Com- 
pany builds a number of welding machines among which is 
the Duograph, designed for the rapid welding of the longi- 
tudinal seams of steel drums, pressure containers and smaller 
parts. The machine comprises a two-arm turret work-holding 
device with water-cooled clamps for holding the steel sheet firmly 
in position while welding. The machine is semi-automatic in 
operation, the torch being traversed by power feed while the 
operator removes the welded barrel and replaces it with a rolled 
sheet to be welded on the opposite arm. The carriage supporting 
the torch is provided with variable feed in order to adapt it to 
the variable conditions of welding. Obviously, the speed of 
traverse must be gauged closely in order to weld perfectly, 
producing neither cold shuts due to excessive speed or burned 
metal because of too slow speed. One torch only is needed for 
light machine welding but the carriage of the Duograph pro- 
vides for the use of two torches, one below and the other above 
the seam. Both torches are used on the thicker gauges which, 
of course, can be welded more rapidly and effectively with two 
torches working on oppvosite sides than when one torch only is 
in operation. 

Machine Welding Torches 

Special forms of torches are used on welding machines, 
the tips being set in line with the axis of the body or barrel. 
The head is water-cooled by means of a water circulation sys- 
tem. The water is conveyed to the torch head by one hose and 
carried away by another. Water cooling is necessary on account 
of the radiated heat which would make the head so hot that 
flashbacks would continually interrupt the work. The tips used 
are special, generally being made to produce a row of flames, 
or a wide thin flame. The row of flames or the long dimension 



of the thin flame, are in line with the joint of course. The 
thin torch flame is called a ribbon flame. 

The No. 1 Duograph which welds a 36-inch seam and han- 
dles containers of 13 inches to 36 inches diameter operates at a 
welding speed of 18 inches per minute and up on No. 16 gauge 
sheets. Very much faster welding has been accomplished on 
special tube and boiler welding machines. So rapid is the weld- 
ing on special machines that pipe and tube manufacture by gas 
welding is becoming an important industry. 

Clamping Work for Machine Welding 

One of the difBculties in the way of machine welding by 
progressive torch action is local heating and resulting expansion 
and subsequent contraction. Expansion and contraction tend to 
cause warping and buckling which, perhaps, cannot be per- 
mitted in the welded product. The faster the welding is ac- 
complished, however, the less the distortion produced, and thus 
the effort in designing welding machines is to provide for as 
rapid welding as possible for two very good reasons ; the first 
being that just mentioned and the second, of course, being greater 
production and reduced cost. 

The distortion produced by the welding flame is also mini- 
mized by firmly clamping the sheets each side of the seam close 
to it. When thus firmly held by water-cooled clamps the sheet 
metal expansion will be' chiefly toward the joint thus having 
the effect of filling the joint with adding material produced by 
the parent metals. The longitudinal expansion is slight and 
hence warping troubles are largely minimized. 

Special Welding Torches for Machine Use 

Other forms of welding torches developed greatly increase 
the speed of welding but they are generally highly special and 
may not particularly interest the hand welder but although you 
probably will never do machine welding it is highly desirable 
that you know something of the great manufacturing possi- 
bilities of the oxy-acetylene machine torch. Remember, that the 
manufacturers of welding apparatus are constantly improving 
their products and that many valuable helps come to men who 
have ideas of their own or who have been forced to resort 



to peculiar metTiods in order to accomplish difficult welding. The 
wide-awake welder will study the principle of the torch not only 
when operated by hand but when mechanically supported and 
guided. This is an era of automatic and semi-automatic ma- 




MIDGET EBONY AND GARNET HOSE 




EBONY AND GARNET LOW PRESSURE HOSE 




BLACK GIANT HIGH PRESSURE HOSE 




STANDARD LOW PRESSURE CORRUGATED HOSE 







STANDARD HIGH PRESSURE CORRUGATED HOSE 

Davis Bournonville Institute 



FIG. 2. HOSE FOR HAND AND MACHINE WELDING AND CUTTING 

TORCHES. 

chinery and oxy-acetylene welding and cutting apparatus will 
doubtless be greatly developed and improved and many applica- 
tions be made that have not yet been thought of. The recon- 
struction of the world following the war gives the general sal- 
vaging of machinery an economic aspect that it never had before. 



Machine Welding Pipe Joints 

Oxy-acetylene welded pipe joints in city industrial plants 
are no longer a novelty but, nevertheless, comparatively little 
pipe has been welded to that which will eventually be welded 
when all the advantages of welding practice are more fully 





CLOTH INSERTION 4 PLY LOW PRESSURE HOSE 





STANDARD LOW PRESSURE CORRUGATED WIRE WOUND HOSE 





STANDARD HIGH PRESSURE CORRUGATED Wl RE WOUND HOSE 





STANDARD COPPER ARMORED HOSE 



Davis Bournonvllle Institute 



FIG. 3. HOSE FOR HAND AND MACHINE WELDING AND CUTTING 

TORCHES. 

realized by city and industrial engineers. Ordinary screw pipe 
connections are unsatisfactory for two principal reasons. First 
and most important is the fact that a screwed pipe joint is 
always likely to spring a leak. If the leak develops in a long 
line it is generally a matter of considerable difficulty to dis- 
connect and make the leaky joint tight. In the second place, 
screwed pipe joints are costly, the ends of the pipe must be 



8 



threaded in pipe machines and the coupHngs made and threaded 
also. But this is not the end of the expense. The job of 
screwing pipe together is slow, hard and laborious, especially 
on pipe of large diameters. 

Special gas welding machines have been developed for weld- 
ing pipe that operate with wonderful speed and efficiency. The 
machine embraces the pipe at the joint and directs a ribbon 
flame against the joint all around the circumference at once. 
Fusion and welding takes places in a few seconds. Means 
are provided for pulling the pipe ends firmly together and up- 
setting them slightly when the metal reaches the fusion stage, 
thus making a perfect weld' slightly thicker at the joint than 
in the unwelded parts. Welded joints make a pipe line one long 
pipe without a coupling, union or other other connection to leak 
and give trouble. The welds are quickly made with the gas 
welding machine at a comparatively small expense and as the 
weld adds practically nothing to the pipe diameter there is no 
interference with the application of pipe coverings. This is 
an important consideration in the erection of steam lines which 
must be heat insulated. The advantages of a smooth non-leaking 
pipe line offset many times the apparent disadvantage of having 
a pipe that cannot be taken apart except by cutting. While is 
is true that the plant engineer ordinarily has in mind the ques- 
tion of possible disconnection, the need of providing for easy dis- 
connection is largely eliminated with welded pipe. In case welded 
pipes must be disconnected the cutting torch, of course, makes 
easy the removal of a section when required for changes. Hence, 
it may be that the pipe fitter of the future will use welding and cut- 
ting torches of common and special forms more than the time- 
honored pipe tongs and pipe cutters. 

Pipe welding is only one of the many applications of gas 
welding torches. It is quite possible that the riveted seams in 
steam boilers and other pressure containers may be displaced 
eventually by welded joints. The possible savings of time, labor, 
material and weight are important considerations but boiler seam 
welding can be realized only with the use of welding machines 
because hand welding is generally too slow and inefficient to 
permit of its use on steam boilers in competition with riveting. 



Questions 



1. Are welding machines suited to repair work? Why? 

2. For what general classes of welding are welding ma- 
chines used? 

3. What is the general difference between a machine weld- 
ing torch and a hand welding torch? 

4. If you were given a contract for laying 5000 feet of 2- 
inch pipe in a skating rink what methods would you 
seriously consider for uniting the pipe? 

5. Is adding material used in welding machines ? 

6. Is a machine torch zig-zagged across the joint? 

7. Why are special tips used on welding machines to give 
a ribbon-like flame? 

8. Why is it necessary to provide water cooling for machine 
welding: torches? 



10 



Notes 



11 



Copyright 1919 by the 
DAVIS-B0URNONVI1.T.E Company 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

TESTING WELDED JOINTS 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by th« 
Davis-Bournonvii^le Company 



TESTING WELDED JOINTS 

Surface Indications of Welding Jobs Uncertain — Test of Oxy-Acetylene 
Welded Joint Training and Character of Man Who Welded It — Effect of 
Testing Welds — Welder Like a Bricklayer, As He Must Begin on a Sound 
Foundation — Factors of Safety — Efficiency of Welds — Pulling and Bending Tests 
— Etching Welds. 

Welded joints, whether made by a blacksmith, an electric 
welder or an oxy-acetylene torch operator may be very fair on 
the surface and rotten at the core. When a weld is finished an 
inspector can check its integrity by the surface appearance only. 
If the surface appearance is good the conclusion is naturally 
drawn that the whole weld is sound, but the conclusion may be 
far from the fact. There is no practical method available by 
which the integrity of any weld can be proven except by break- 
ing it or pulling it apart. Of course, any method of testing 
welds that requires their destruction is out of the question for 
comrnercial work. 

Test of Oxy-Acetylene Welded Joint Training and 
Character of Man Who Welded It 

The test of the weld is the character of the man who made 
it. Hence, the testing of welds must resolve into a matter of 
training welders to make sound welds and then depending on 
their sense of honesty to follow the methods taught when doing 
commercial work. In the workroom exercises you have noticed 
that you have been required to break apart almost every weld 
made, and to note the defects common in the work of oxy-acety- 
lene welding beginners, and to distinguish between good and 
poor penetration. You were required to weld test pieces and 
pull them apart in a testing machine. You learned how strong 
a weld actually is when subjected to the test that admits of 
no deception. 

What has been the result of this constant testing of welds ? 
You have learned to be your own severest critic and to correct 



faults of practice that produce poor work. You have learned 
to instinctively reahze when you are getting penetration and per- 
fect union. You know when you have finished a seam whether 
the weld is sound or otherwise, because you have welded similar 
pieces and tested them to destruction. The laws of nature work 
always the same, and if you have followed methods which ex- 
perience has proved' to be sound, you are bound . to get good 
results. Therefore, the practical test of an oxy-acetylene weld 
is the character and training of the man who made it. 

Effect of Testing Welds 

When you made your first welds in thin steel and broke 
them apart you doubtless were much surprised to see how easily 
they parted company. The weld was mostly camouflage ; the 
material was united in spots only and along the edges. It was 
not soundly welded in the center. 

These defects were not at all strange to your instructor. 
He knew that you were a beginner and that you would in- 
evitably make the same mistakes that all make when learn- 
ing the art. There are many things to master in oxy-acetylene 
torch practice, and it is too much to expect that any ordinary 
human being will master all of them at once, and apply the 
principles correctly. He has to learn by experiences and prac- 
tice to hold the torch in the correct position and give it the 
proper motion so that he can concentrate his mind on produc- 
ing a puddle and feeding it with adding material. At first you 
made the mistake of melting your adding material with the 
torch flame and produced welds containing cold shuts and piled 
up metal. You finally learned that the puddle must melt the 
adding material, which means that the torch flame may be so 
held as to produce the fusing temperature in the metal. If 
the puddle is hot enough to melt the adding material, you may 
be sure that it is hot enough to fuse the sides of the plate and 
produce intimate union when cold. 

Welder Like a Bricklayer as He Must Begin on a 
Sound Foundation 

As you improved in practice your welds became stronger 
and you learned that you were like a bricklayer — you have to 



work up from the bottom, begin on a sound foundation, and 
every layer has to be deposited with care. If you start rig'ht 
at the bottom and work right clear up to the top you must pro- 
duce a sound job, and there can be no question but that the 
weld will be strong. 

When your welded joints were tested you found that some 
of the best appearing joints failed much easier than some of 
the others that were rougher and not nearly so attractive. The 
oxy-acetylene welded joints are like men. Some men have 
smooth, polished exteriors but are rotten at the core ; they have 
little strength of character and their principles are bad. Other 
men of rougher exterior may be sound and dependable. Their 
word is good as their bond, and if they undertake to work for 
an employer they give him the best service they are capable 
of rendering. But do not assume that it is not good prac- 
tice to make smooth, fine appearing welds. On the contrary, 
it is highly desirable but we want you to learn first of all 
to make a sound weld no matter how it looks, and then to 
make a sound weld of good appearance. 

Factors of Safety 

Fortunately, for much welded work, the factor of safety is 
hig'h. By factor of safety we mean that the actual load or 
stress that a part must sustain is a fraction of the actual strength. 
The actual strength is several times the strength required. For 
example, pressure containers like steam boilers are usually made 
of steel plates having five times the highest tensile stress that 
will be imposed by normal steam pressures. Then the factor of 
safety is five; that is, the shell could be subjected to a pressure 
five times the normal before it would give way, If the working 
pressure were 150 pounds per square inch the boiler might not 
explode until the pressure runs up to 750 pounds per square inch. 

So it is in general with machine members and other parts 
that fail in service due to accident. They were designed with 
liberal safety factors to provide for several times the normal 
load but shock, wear or accident has caused failure. The welder's 
job may last long even though the weld is actually weaker than 
the original part, but he should always try to reach 100 per 
cent efficiency. 



Eificiency of Welds 

When making welds for tests do not deceive yourself or 
anyone else by making the welded part thicker than the re- 
mainder of the bar. In practice it may be desirable to increase 
the cross section of the welded part in order to insure the maxi- 
mum strength, but when you are welding to test your efficiency 
be frank with yourself and build up the joint to the thickness 
that when smoothed off its dimensions will be the same as the 
bar and' no more. Then, when the bar is pulled in the testing 
• achine you will know definitely what the percentage strength 
c the weld is. 

By 100 per cent efficiency we mean that the welds will be 
as ;trong as any other part. A mild steel bar J^ inch thick and 
2 inches wide should have an ultimate strength of about 60,000 
pounds. Now, if you are ever able to weld a steel bar ^^ inch 
thick and two inches wide, making the weld no thicker than 
the bar and have it withstand a pull of approximately 60,000 
pounds, you have reached 100 per cent efficiency. The bar will 
break in some other place as quickly as in the weld. How- 
ever, 100 per cent efficiency in an oxy-acetylene welded joint or 
any other is too much ever to expect. If you get up to about 
95 per cent you will be doing very well indeed, and that is 
about as much as any one can reach. The welded joint is built 
up of fused material and, of course, fused metal is never as 
strong as the rolled metal of the same grade. 

Pulling and Bending Tests 

Pulling a welded joint apart in a tensile testing machine de- 
termines the strength of a weld under direct pulling stress. Many 
welded joints show a high tensile, strength even when composed 
largely of brittle adding material. A brittle metal like cast iron 
even may develop comparatively 'high tensile strength when pulled 
apart under favorable conditions. The tensile or pulling test is 
not always, therefore, a dependable test of welded joints, especially 
if it is likely to be subjected' to alternate bending stresses. The 
shell of a pressure container like an air receiver may be subjected 
to many slight bending stresses due to alternate filling and dis- 
charge. A welded longitudinal joint in such a container must be 
free of brittleness. 

6 



Bending a, welded steel bar is a more severe test of the in- 
tegrity of the weld than the pulling test. If the adding material 
has been slightly oxidized and made brittle the bending test will 
disclose it, and if the penetration is poor the defects will be made 
apparent. You will find decided difference in the strength of 
welded joints depending on which way you break them apart when 
held in the vise. If you break a prepared joint weld apart so as 
to tear the metal on the top side of the joint apart it will generally 
offer considerably more resistance than when broken in the op- 
posite direction. Hence, when testing thin welded specimens i 




TESTING STEEL PLATE WELDS IN THE VISE "wiTH THE WELd" AND 
"against THE weld" 

the vise you should put them in the vise jaws with the lower side 
toward you. Then the hammer blow will stress the lower part of 
the weld most and thus give you an excellent test of penetration. 
If you always test the other way you may deceive yourself be- 
cause you are not giving a bending test that brings out the defects 
of penetration. 

The bending test is crude but effective for rough and ready 
comparison, and is excellent for beginners. The pulling test in a 
tensile machine has the advantage of giving the stress in pounds 



required to produce rupture, and a series of welds can be pulled 
apart and the data recorded for future reference. The bending 
test made in a vise gives you no figures for record. Bending tests, 
however, may be made in the testing machine by reversing the 
machine and supporting the specimen on blocks a certain distance 
apart, and applying the load in the center over the weld. The 
pounds pressure applied, the distance between the supports, and 
the angle or drop in inches at which the weld gives way should be 
recorded. 

The vibration testing mac'hine also provides means for mak- 
ing bending tests and giving a record that is useful for comparison 
now and in the future. The vibration machine holds the sample 
firmly at one end in a vise or clamp while the other end is vibrated 
to and fro a short distance by means of a ram connected to an 
adjustable crank on a rotating shaft, or an equivalent device. The 
machine is started and run until the specimen breaks when an 
electrical apparatus stops the machine. The counter shows the 
number of vibrations required to break the sample. The ampli- 
tude of the vibration can be changed to suit the thickness and 
length of the specimen to be tested. 

Etching Welds 

Although it is substantially correct that surface indications 
are not a true index of the strength of gas welds, there are, 
nevertheless, certain appearances that on an average do indicate 
to the trained man what the probable characteristics of a weld 
tested to destruction will disclose. The welder should, therefore, 
develop to as high a degree as possible the ability to find surface 
defects in welded joints and from these defects be able to judge 
the probable condition of the joint as a whole. The presence of 
mottled or shiny metal discloses the use of carbonizing or oxidiz- 
ing flames which mean weak material in the joint. Irregular 
welding and filling are evidences generally of poor torch manipu- 
lation, and probably lapping, cold-shuts and poor penetration will 
be found by destructive tests. In addition to destructive pulling 
or bending tests the practice of etching the end of the joint of 
test specimens will be very useful in educating a welder to de- 
termine the probable defects from surface indications. 



To etch a weld the specimen should be cut across the joint 
and the surface should be filed, polished and buffed perfectly 
smooth. It is then corroded with an etching fluid suitable for the 
metal and after a few seconds it should be cleaned off and ex- 
amined. A great change will be noticed. The parent metal and 
adding material will be clearly defined and the line between them 
will have characteristics that tell whether or not fusion and 
interlocking were accomplished. 

Etching a weld of course tests only the section etched, and 
proves nothing regarding the character of the joint on either side. 
But it in general will prove to be a pretty accurate index of 
what has taken place elsewhere. Breaking welds apart with the 
hammer, pulling them apart in the testing machine and etching 
specimens are useful exercises for every welder to practice. They 
impress on him the fact that sound welds can be produced only 
by following sound practice. The torch flame must be properly 
adjusted, the right size tip must be chosen for the thickness of the 
metal, the manipulation must be even. The welding must not be 
hurried too fast nor should it be allowed to dawdle along. If the 
work is hurried the weld will be full of cold-shuts and laps, and 
if done too slowly the imetal is likely to be oxidized and weak. 



Questions 



1. What percentage of strength may be reasonably ex- 
pected in a sound gas welded joint in mild steel? 

2. What conclusion would you draw if the surface of a steel 
weld is shiny and covered with oxide? 

3. What would you deduce if the weld is mottled and pitted 
on the surface? 

4. How should a welded' joint be broken apart in a vise? 

5. What is the proper method of breaking apart to make a 
severe test of penetration? 

6. Is the tensile test a conclusive test of strength in a 
welded joint? 

7. What will the bending test generally disclose? 

8. What is the effect on a welder of testing his own welds 
to destruction? 

9. Why is a brittle weld unsafe in a machine member? 



10. What does the etching test show ? 

11. How would you prepare a specimen for etching? 

12. How should you line up a test bar for welding? 



10 



Notes 



11 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

BRAZING 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 sy th« 
Davis^Bournonvilt,e Companv 



BRAZING 

Brazing an Ancienl Art — Bunsen Burner or Torch Effective for Brazing — 
dose Fitted Joints Important — Malleable Iron Brazed Instead of Welded— Silver 
Solder. 

Uniting brass, bronze, copper and other metals with molten 
spelter is a very old art dating from pre-historic times. Brazing 
is soldering, the solder having a much higher fusing temperature 
than ordinary tinner's solder and being much stronger and harder ; 
it is for that reason called hard soldering. Spelter is another name 
for zinc but brazing spelter is not pure zinc. The spelter used 
for brazing is an alloy of zinc and copper, generally in about 
equal parts, but the ratio is varied to suit the metals to be brazed. 
Hard solders should have lower fusing temperatures than the 
metals to be united as otherwise the heat required for melting 
the spelter is likely also to melt the parts and cause complete fail- 
ure of the job. This injunction applies particularly to brass jobs 
that must be done in open forges, gas furnaces or with other 
sources of heat which cannot be applied locally but must heat the 
whole piece. 

Bunsen Burner or Torch More Effective Than 
Furnace 

When working with the Bunsen burner torcTi the workman 
can braze much more efifectively than in a furnace as he may 
direct the flame on the joint only and heat but little more of the 
adjacent metal than is required to fuse the spelter and produce 
amalgamation. In general, then, the use of gas burners and torches 
is preferable for brazing to any other method of heating. Less 
heat is required and less damage is likely to be done than when 
the parts must be raised throughout to the melting temperature of 
spelter. Uniting parts by brazing is an operation that an all- 
around welder must frequently perform. It is distinctly ad- 
vantageous to braze often times and should be practiced when 
the result will be a more satisfactory job than welding. 

3 



Joints for Brazing Should Fit Closely 

There is one feature of brazing in general that differs 
radically from the practice you have been taught in regard to 
oxy-acetylene welding and that is the need of close fitting in order 
to get best results. When preparing for gas welding you must 
open up the joint by beveling the edges in order to produce a 
perfect weld. But in brazing the closer the parts to be brazed 
are brought together the better the result will be, strange as it may 
seem. When two parts are to be brazed they should be fitted 
closely even though it may take considerable filing to accomplish 
this. For instance, if a steel plug is to be brazed into the mouth 
of a pipe the scale should be removed from the interior of the pipe, 
and the plug should be turned or filed to fit closely. Even if you 
have to drive the plug into the pipe with a hammer do not be 
afraid that the spelter cannot get in and form a sound joint. 
It is a peculiarity of molten spelter in contact with hot .metal 
that it will penetrate into the most closely fitted joint. The 
closer the joint and the more accurate the fit, the stronger the 
brazing. 

Hence, if you are called upon to braze a lug to the side of a 
frame which has been riveted and the rivets have worked loose, 
do not attempt to braze the joint before tightening the rivets, if 
they can be tightened. If the rivets cannot be tightened, draw 
the lug against the frame as closely as possible by means of a 
C-clamp and then braze to the frame and around the rivets. You 
will produce a much better job with a thin filling of spelter than 
you could possibly get if you tried to fill a gap 1/16 inch wide or 
more. 

Clean Thoroughly Before Brazing 

A precaution that must always be observed when preparing 
for brazing is to thoroughly clean the parts of oil and grease. 
In the case of a loose lug considerable time may be required to 
get all the grease and oil and dirt from underneath the pad before 
you are ready to braze. Use plenty of gasoline or kerosene to 
clean out the joint and then clamp firmly in place and heat slowly 
to dry out the joint. If possible, the metal parts in contact should 



be brightened with a file to remove all rust and oxide deposits. 
You cannot possibly produce a good job of brazing when the 
parts are corroded, rusty and dirty. 

Use Wire Spelter for Torch Brazing 

When ready to braze the joint should be sprinkled with 
powdered borax, or better, with an approved brazing flux and 
then the torch flame should be played on the plates to heat them 
up but without producing local fusion. In other words, do not 
hold the flame steadily in one place long enough to cause the metal 
to melt. Move it back and forth until the temperature has been 
raised to a point somewhat above the melting temperature of 
the spelter. Wire spelter is very convenient for many situations 
and a supply should always be kept on hand. You can apply the 



BRAZE WITH BRONZE 
AND REINORCE 




-CRUDE WROUGHT IRON SKIN 



BLACK HEART 



Davis Bournonville lns;iUite 



FIG. 1. BRAZING A BROKEN MALLEABLE CAST IRON LEVER. 

wire spelter the same as wire solder and often you will be able 
to do a smooth, clean job of brazing that would be very diflicult in- 
deed, if you used the granulated spelter because of the difficulty of 
applying it where needed. 

When the spelter flows and runs into the joint it spreads 
very quickly, and the job may be done before you Icnow it, es- 
pecially if the parts are closely fitted together. Little spelter will 



be needed then; when it begins to flow keep watch of the under 
side to see when it penetrates and appears. As soon as the 
spelter appears to be spread through the joint turn off the torch 
and let the job cool under the protection of some non-conductor 
of heat like asbestos paper. If asbestos paper is not available, 
any protector at hand should be used in order to prevent severe 
cooHng stresses being produced that might warp the parts or 
fracture them. 

The brazing produced with the ordinary grades of spelter 
will do very well for uniting brass and copper but if you are going 
to unite steel parts by brazing and the job requires considerable 
strength it will be advisable to use bronze welding wire and braze 
at a higher heat. The joint produced by molten bronze will be 
very strong and it will have an advantage important sometimes 
that the heat required is several hundred degrees less than re- 
quired for fusion welding of steel. 

Broken Malleable Castings Should Be Brazed 

We have spoken about the difficulty of welding broken malle- 
able iron castings, and have advised brazing instead wherever 
possible. This is a case evidently for which brazing is superior 
to welding, because unfortunately welding requires so high a 
heat that the malleable iron is changed to a poor grade of cast 
iron, and the resulting welds is necessarily weak and faulty. On 
the other hand, a well brazed joint will be as strong as the original 
casting, or stronger. A broken malleable casting should be pre- 
pared for brazing by first thoroughly cleaning and removing all 
rust and foreign matter. If the parts are thick it may be ad- 
visable to bevel the edges slightly in order to confine the molten 
spelter and direct it into the joint. When the parts are thin no 
beveling is necessary but when thick and of considerable cross 
section area the amount of spelter required may make beveling 
desirable. The bevels provide troughs and prevent the unde- 
sirable spread of the brass over the surface. The beveling should 
be cut so as to leave "witness" or location parts untouched by 
which the alignment can be fixed and maintained. When the 
joint is filled the troughs produced by beveling should also be 
filled in order to make a smooth surface. 



When brazing malleable iron use a bronze welding wire and 
bronze welding flux. The bronze wire will make a stronger bond 
than an ordinary spelter and in general, as has been previously 
stated, it should always be used in brazing parts that require 
high tensile strength. Use the ordinary wire spelter only for 
brazing parts requiring low tensile strength and which might be 
injured by the high fusing temperature required for the bronze 
wire. 



^ ^%^%%-^^ m%^ ^y-^/^'^" ^°^°"^° ^°'^^^ 




CUTTING OXYGEN 




PREHEATING OXYGEN 



ACETYLENE 



Davis Bournonvllle Institute 



FIG. 2. SILVER SOLDERED JOINTS IN A TORCH HEAD. 

Spelters or brazing metals are generally copper and zinc al- 
loys consisting of about equal parts of copper and zinc. Spelter of 
this grade melts at about 1600 degrees F. The higher the copper 
content the higher the melting temperature. Spelter containing 
four parts copper and one part zinc melts at about 1850 degrees 
F. On the other hand, spelter containing one part copper and 
four parts zinc melts at 1300 degrees. The one to one alloy 
combines strength and a comparatively low melting temperature. 



Silver Soldering 

Silver solder is another strong hard solder very useful for 
new work and repairing. A flux should be used to protect the 
metal and the parts to be soldered should be clamped together with 
sheet silver solder between and slowly raised to a red heat with the 
torch at which temperature the silver will fuse and unite with the 
steel. A silver soldered joint is very strong when properly made 
and will stand repeated bending stresses, thus fitting it for band 
saw repairs and other work subjected to bending and shocks. 

The welder who learns to braze in order that he may use it 
when desirable should know that the fumes rising from brass, 
spelter and zinc are poisonous and should not be inhaled. Brazing 
should not be long continued in a small closed room. Work near 
an open window or in a large room well ventilated when doing a 
heavy brazing job. Also use care in heating as the torch flame 
temperature is far above that required to melt brass and spelter. 
When you see white fumes rising reduce the heat by removing the 
torch flame. The zinc is burning out of the metal, weakening its 
structure and poisoning the air. 

Questions 

1. What is common spelter? 

2. Why is spelter called hard solder? 

3. Why is the torch more effective for brazing than a forge 
or furnace? 

4. How should brazed joints be fitted? 

5. What effect have grease and rust on brazing? 

6. Which is the best for torch brazing— granulated or 
wire spelter? 

7. Why braze malleable iron ? 

8. Is a brazed joint reliable? 

9. What is silver solder used for? 

10. What should be done about ventilation when brazing? 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



GAS, ELECTRIC AND THERMIT 
WELDING 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY. N. J. 



Form 393 




^■SX-^ |Tdrop bottom "^*2) 



WIND BOX 
BRANCH 



o 

LADLE 



Davis Bournonville Institute 



Fig. 1. THE FOUNDRY CUPOLA SOMETIMES USED FOR 

"burning on" 



GAS, ELECTRIC AND THERMIT WELDING 

Oxy-Acelylene Apparatus Readily Portable and Low Priced — Electric Weld- 
ing of Two General Types — Spot Welding Essentially a Manufacturing Process — 
Electric Arc Produces Dazzling Light — The Goldschmidt Thermit Process — Thermit 
a Compound of Aluminum and Iron Oxide — Preparation for Thermit Welding — 
Pouring the Tremit Steel — The Oxy-Acetylene Welder Should Not Undertake Im- 
practical Jobs. 

Gas, electric and thermit welding processes are compara- 
tively new developments and in a sense they are competitive 
methods of uniting metals by fusion but the competition is more 
apparent than real because each type of welding is in general 
suited only to its own field. There is some overlapping of the 
field's, of course, but each has its own pretty clearly defined 
lines of work. Gas or oxy-acetylene welding is preeminently 
the means for doing general repair work of which there is always 
a great quantity and now exceptionally an enormous amount espe- 
cially in the devastated regions of Europe resulting from the 
wreck of war. The electric welding processes are, in general 
suited to manufacturing chiefly and the thermit process is, a re- 
pair process for welding thick heavy metal sections. 

Oxy-Acetylene Apparatus Portable and Low-Priced 

The oxy-acetylene process of welding is suited to both manu- 
facturing and repair work. It has advantages for repair work 
over all others. The apparatus is readily portable, compara- 
tively low priced and may be used in almost any situation or 
location. It is preferred by general repair shops, garages, ma- 
chine shops, field repair gangs and jobbing shops having a 
variety of repairing to be done under all kinds of conditions. 
The welds produced with the oxy-acetylene torch when manipu- 
lated by a skilled welder are considered generally superior to 
the welds made by the electric arc process, having greater elas- 
ticity and density. The apparatus for field use is self-contained con- 
sisting of two cylinders with their regulators and pressure gauges, 



the hose and the torch only. The accessories required are few and 
easily transported. It is usable in remote regions where no elec- 
tric current is available and the heaviest welds are within its 
scope. However, w'hen it comes to very heavy welding, the 
question arises whether the cost may not exceed the cost of 
thermit welding. The oxy-acetylene welder should believe thor- 
oughly in his process but he should recognize its limitations on 
heavy work and exercise judgment when asked to estimate on a 
heavy repair job. 

Electric Welding of Two General Types 

The electric welding process is of two general types — spot 
and arc. Both operate on the same principle, fusion being pro- 
duced by the heat transformation of an electric current. When 
a current passes through an electric conductor the tempera- 
ture rises owing to the resistance. The rise in temperature may 
not be perceptible in an ordinary wire or cable as a wire having 
comparatively large cross section is a good conductor. The cur- 
rent flowing meets with insufficient resistance to raise the tem- 
perature much about that of the surrounding atmosphere. But 
if the quantity (amperage) of electricity flowing through a wire 
is suddenly raised say ten or twenty times the normal and the 
wire would quickly get hot and perhaps fuse with a blinding 
flash and loud report. This is what happens when a fuse blows. 
The fuse is a safety device made of metal of low fusing tem- 
perature, and' is so proportioned that it breaks down before the 
conductor itself is greatly overloaded. 

Electrical heat is proportional to the electrical resistance; 
if the conductor offers high resistance to the passage of cur- 
rent it becomes hot and finally reaches the fusing temperature 
if current of sufficient strength is long supplied. Fusion pro- 
duced by electric heat is thus the basis of electric welding. The 
heat results from a series of transformations. It is first pro- 
duced generally by the burning of coal under steam boilers in 
a power house. The burning coal generates steam which drives 
the engines or turbines which, in turn, drive the electric gen- 
erator. The electric current produced is transmitted by wire 
to the welding macbine where meeting with excessive resistance 



the energy reappears in the form of heat, producing fusion and 
welding. In oxy-acetylene welding, the heat required for fusing 
is produced by combustion of acetylene in an atmosphere of 
oxygen. 

Spot Welding Essentially a Manufacturiug Process 

Spot electric welding is essentially a manufacturing method 
of uniting thin overlapping metal parts. Spot welds are made 
in spots by two opposite copper electrodes which are pressed 
against opposite sides of the sheets to be welded with consider- 
able force and held for a few seconds while the current flows 
from one electrode to the other through the metal. Fusion is 
produced in a small spot and the two sheets are almost in- 
stantly welded by the pressure of the electrodes which forces 
the fused metal between them intimately together. Spot welds 
are strong and are well suited for many kinds of s'heet metal 
products not requiring water-tight seams. They are used, some- 
times for the fabrication of pressure containers also which after- 
wards are brazed or soldered in the seam to make them liquid 
or gas-tight. 

The electric spot welding process is advantageous for uniting 
galvanized or tinned sheets as it is not considered good prac- 
tice to gas weld galvanized iron or tin. When fused under 
the torch zinc and tin unite with the steel and produce a weak 
metallic structure. If you are ever required to gas weld gal- 
vanized metal with the torch be careful to clean all the zinc 
or tin off mechanically or with acids before fusing the metal. 
The same precaution should be taken with tin sheets. A welded 
tin sheet will be so brittle if welded without removing the tin 
that it may break apart with a slight blow. 

Electric Arc Produces Dazzling Light 

When a strong electric current flows from one metallic 
conductor to another it tends to persist when the conductors 
are separated. The current jumps through the air, produc- 
ing great heat and dazzling light. The heat is so intense that 
metal electrodes are molten almost instantly. The electric arc 
welding process is based on this principle and is capable of wide 



application. It is a strong competitor of gas welding in manu- 
facturing, shipbuilding, car building and fabricating plants. But 
it has some disadvantages which must be frankly recognized. 
In the first place, arc weld's are not generally as strong as those 
produced by the oxy-acetylene torch. The welds are more brittle 
and porous. Arc welds, therefore, are not suitable for pressure 
containers made of thin metal because the joint is likely to be 
brittle and full of small holes. The porosity of arc welds 
varies with the electrodes used, but whether much or little it 
is likely to give trouble when the containers are made to trans- 
port gasoline and other volatile liquids. The porosity will, under 
some conditions, give trouble also in thick welds subjected to 
high heat and pressure. Superheated high pressure steam will 
escape through a porous electric weld of considerable thickness- 
The second important disadvantage of the electric arc proc- 
ess is the intensly dazzling light produced which is very danger- 
ous to the eyes if unprotected by colored glasses. The light 
is not only dangerous to the welder himself but to other work- 
men nearby who may, in an unguarded moment, look directly 
at it. A short exposure of the eyes unguarded by colored 
glasses close to the electric arc may result in partial or total 
blindness. This, from the standpoint of the workman is a most 
serious drawback to the use of the electric arc in manufacturing 
and fabricating plants. The welder must never work without 
protecting the eyes and even with the best eye protectors some 
welders suffer from eye troubles. The ultra violet rays also 
penetrate thin clothing and often burn the flesh on the body pro- 
ducing the same effect as sunburn. 

Two Methods of Electric Arc Welding 

There are two general methods of using the electric arc 
for welding. In one the metal is fused with a carbon electrode 
and adding material is fed to the joint the same as with the oxy- 
acetylene process. In the other process a metallic electrode is 
held in an insulated holder and the current fuses the electrode 
itself and deposits the metal in the joint as it drops from the 
end. This method has the advantage of employing only one 
hand but as the welder generally holds a screen of colored glass 



before the eyes with the other hand, both hand's are employed. 
When welding with metallic electrodes the end of bare elec- 
trodes must be held at a certain distance from the work. If 
the distance is too short a short circuit results and if too great 
60 to 110 for wrapped electrodes. With alternating current and 
bare electrodes an open circuit voltage of 125 to 150 volts is 
the arc is broken. Considerable manipulative skill is required, 
therefore, to weld successfully with bare electrodes. The 
common diameter of the bare electrodes is /^ inch, and the 
current values range from 75 to 250 amperes, depending on 




A MAGNESIA STONE 

B MAGNESIA THIMBLE 

C REFRACTORY SAND 

D METAL DISC 

E ASBESTOS WASHERS 

F TAPPING PIN 



Davlsj'ocrracouville InstilDte- 



FIG. 2. SPECIAL CRUCIBLE FOR THE REACTION AND POURING 
OF THERMIT STEEL 

the thickness of the plates. From 150 to 200 amperes are 
generally used with the ^^ inch electrode. The open circuit 
voltage for direct current should be between 35 and 110 volts. 
For bare and coated electrodes 35 to 75 volts are required, and 
necessary with resistance control, and 110 volts with reactance 
control. If an internally regulated transformer is used open 
circuit voltage under 110 volts produces an arc that can be 



readily controlled. Whatever the current used the regulation 
should be such that the current will not increase over 50 per 
cent when the electrode touches the work and the arc is thus 
short-circuited. 

From the foregoing you will realize that the electric arc 
process requires special apparatus and considerable technical 
knowledge on the part of the one in charge, as well as skill 
on the part of the operator. 

The Goldschmidt Thermit Process 

The third important modern method of welding is the ther- 
mit process developed some years ago in Germany by Gold- 
schmidt. It is one of the interesting developments of chem- 
istry in which finely powdered aluminum plays an important 
part with iron oxide. It is essentially a casting process analog- 
ous to "burning on" in a foundry, requiring a mould into which 
the molten steel is poured around the broken parts to unite them. 
The thermit process is eminently suited for making heavy re- 
pairs and is generally used for welding broken rudder posts, 
stern frames, locomotive frames, engine crankshafts, propeller 
shafts, heavy castings and in general, work having large cross 
sections. The time and labor required to prepare for thermit 
welding is considerable. But the actual pouring of the molten 
metal which forms the weld requires but a few second's. 

Thermit Composition of Aluminum and Iron Oxide 

The mclten steel results from the chemical reaction of 
thermit, which is the name given to a mixture of finely divided 
or powdered aluminum and iron oxide. Aluminum, as you know, 
has a strong attraction for oxygen and unites with it rapidly when 
raised to the fusing temperature. The reason that aluminum 
does not rust like iron is that the thin oxide coating on the 
surface protects the metal beneath and prevents the oxidizing 
action from progressing. Iron oxide, however, does not protect 
the metal beneath and so the rusting process continues indefinitely 
until the metal is completely oxidized. The aluminum in the 
thermit mixture robs the iron oxide of its oxygen when the re- 
action has once been started by heat and produces aluminum 



oxide and molten steel. The reaction takes place with such 
rapidity and intensity that a temperature of about 5,400 de- 
grees E. is produced. So intense is the heat that it is sufficient 
to melt about 15 per cent of its weig'ht in mild steel punch- 
ings which are used to increase the amount of molten steel and 
to reduce the temperature. The reaction in the crucible takes 
place in a few seconds when started and the metal is immediately 
poured into the molds. The practice of using thermit for mak- 
ing welds is briefly as follows : 



POURING GATE 




HEATING GATE 
j= FRAME g = FACING '/j FIRE SAND 1/3 FIRE CLAY I/3 GROUND FIRE ERICK 

I = YELLOW WAX ^ = LOAM OR MIXTURE OF % SHARP SAND I/3 FIRE CLAY 
^ = SAND FLOUR CORE 



Davis Bournonville Institute 



FIG. 3. MOULD FORMED AROUND THE PARTS TO BE WELDED 

Preparation for Thermit Welding 

The broken parts to be welded must be lined up the same 
as for oxy-acetylene welding in order that when welded the 
restored part should be of the same shape and dimension as 
before. Sufficient metal must be cut away from the joint to 
permit the molten steel to enter between the ends in sufficient 
quantity to produce fusion and complete union when cold. The 
thickness that must be cut away depends on the size of the parts 
ranging from, say one-half inch up to one or two inches, or 
even more on very heavy sections. 

The parts must be thoroughly cleaned to remove all grease, 
scale and rust. When the parts have been prepared the space 
between them is packed with yellow wax and a reinforcing band 
of wax is molded around the parts thus giving the effect of a 



reinforcing collar. Wooden patterns for risers and pouring gates 
are provided, and a sheet metal box is made for a mold. The 
patterns of the risers and gates are assembled in contact with 
the wax in their proper locations and then a mold of fire sand, 
fire clay and powdered fire brick is made about them, using the 
sheet iron box to hold the mold in place. When the molding 
has been completed the riser and gate patterns are removed 
and the mold and parts to be welded are heated with oil blow- 
torches to dry out the mold, melt the wax and' preheat the 
metal. Provision is made for drawing off the wax as it melts. 
When the wax has been melted out a cavity is left in the mold 
into which the molten thermit steel is poured. The parts are 
preheated in order to prevent chilling of the thermit metal. 

The Reaction in the Crucible 

The mold is now ready for pouring. A special crucible 
having an outlet at the bottom is set up over the. mold and the 
amount of thermit and steel punchings required for the weld, 
with some excess, is charged into the crucible. The outlet in 
the bottom of the crucible is sealed with a sort of tappet valve 
the stem of which projects beneath. A refractory protective 
washer is provided above the valve to prevent premature fusion 
and discharge of the contents. The chemical reaction in the 
thermit charge is started by firing a fuse which produces a suffi- 
ciently high temperature to start the reaction of the aluminum 
and iron oxide. When once begun the reaction spreads rapidly 
and requires only about 30 seconds during which time the alum- 
inum unites with the oxygen of the iron oxide producing alum- 
inum oxide and thermit steel having a temperature of 5,400 
degrees F. As stated, a quantity of mild steel punchings is 
mixed with the thermit to increase the quantity of steel and to 
reduce the temperature of the welding metal. 

Pouring Thermit Steel 

As soon as the reaction is completed, the crucible is tapped 
by raising the valve at the bottom and the molten metal flows 
into the mold at so high a temperature that it fuses the pre- 
heated metal parts and unites them perfectly when cooled with 

10 



a steel casting. The band of wax formed around the parts 
when preparing the mold is reproduced in a collar of rein- 
forcing steel around the weld. Of course, this collar must be 
dispensed with if the break should happen to be in a part that 
must be machined to its original dimension. The spectacular 
appearance of the reaction in the crucible and the remarkable 
results so quickly obtained make thermit welding one of the 
most interesting methods of repairing broken parts. But, as 
stated in the foregoing, it is in general suited only for heavy 
repair work in which field it is preeminent. The oxy-acetylene 
welder should not regard the thermit process as a serious com- 
petitor in a general way as it should be used only for the heavy 
welding that is impractical of repair by other processes. 

The Oxy-Acetylene Welder should not Undertake 
Impractical Jobs 

This brings up an important matter in oxy-acetylene weld- 
ing practice. The welder must learn to estimate the cost of 
welding and to judge if the job offered is one that he can handle 
to the satisfaction of the customer. It is not to his interest to 
undertake to weld with the torch repair jobs that could be better 
handled by thermit welding, neither should he undertake to gas 
weld small parts in large quantities that can be electrically welded 
at lower cost. This does not mean, however, that gas welding 
cannot compete with electric welding in manufacturing, if 
the proper appliances are provided and the work systematized on 
a manufacturing basis. It does mean that the jobbing welder 
should not undertake to do manufacturing on a jobbing basis. 

We have given you in this review of the three modern 
processes of manufacturing a general idea of their scope and limi- 
tations as we believe it is desirable that you know something 
about all of them. You can more clearly realize the limitations of 
your own field as well as its possibilities. The oxy-acetylene 
welder should be enthusiastic but practical. He should not be 
carried off his feet and undertake impracticable jobs. A failure 
is a poor advertisement and a customer will remember a failure 
much longer than many satisfactory performances. 

11 



Questions 



1. What is electric spot welding suited' to? 

2. Is spot welding a repair process? 

3. What are the two principal types of arc welding? 

4. What precaution must be taken in all arc welding in 
regard to the eyes? 

5. Is arc welding essentially a repair process? • 

6. What advantages do you see in the oxy-acetylene 
process ? 

7. What is required to weld a field job with the oxy- 
acetylene torch? 

8. What is the thermit process of welding? 

9. For what is the thermit process best suited? 

10. Would you undertake to weld a 10-inch broken shaft 
with the torch? Why? 

11. What process would you recommend? 

12. What should you do when welding galvanized steel with 
the torch? 



12 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

GAS PIPES AND MANIFOLDS 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonville Company 



GAS PIPES AND MANIFOLDS 

Oxygen Piping — Welded Pipe Lines — Size of Pipe Required for Oxygen 
Line — Safety Valves for Oxygen Lines — Acetylene Pipe Lines — Gas Manifolds — 
Pressure Regulators — Branch Line Pressure Regulators — Copper Must not be used 
in Acetylene Lines — Backfire Chamber or Water Seal for Acetylene Lines — Gen- 
erated Acetylene Supply — Piping Gases to Welding Benches. 

The ordinary gas requirements of the individual welder are 
provided for by drawing from one cylinder of acetylene and one 
cylinder of oxygen at a time. The limitation on the use of gas 
from cylinders applies only to acetylene, the rule being that no 
more than one-seventh of the capacity of an acetylene cylinder 
be used hourly in order to avoid drawing over the acetone. But 
not all gas welding requirements will be properly provided for in 
this manner. You may sometimes have to weld a big job on 
which three or four torches will be working at once which means 
that you will be consuming three or four times as much gas as 
usual. Moreover, in welding shop practice you miist provide for 
the use of torches at several stations, and that means large gas 
consumption, and piping for the gases to convey them throughout 
the plant to the stations. Piping for gas used in oxy-acetylene 
welding and' cutting might be considered to be merely an ordinary 
steam pipe fitting job. But the conditions that must be complied 
with require considerable special knowledge, not possessed by the 
regular steam fitter. 

Oxygen Piping 

We will first speak of oxygen pipe line installations. Ord- 
inary black iron gas pipes screwed together without clear oil or 
grease on the threads may be used for oxygen pipe lines with 
general satisfaction. Soap or a graphite compound should be 
used on all screwed connections of apparatus containing oxygen 
as the use of clear oil alone is considered dangerous because of 
the possibility of some oil remaining inside the pipe and taking 
fire in the oxygen atmosphere. If this should happen the fire 



might continue to burn after the oil was consumed by feeding- cm 
the iron until it became so thin that the walls would burst under 
the pressure. Graphite mixed with tallow, or the graphite com- 
pound gredag are allowable lubricants for screw threads but they 
should be used sparingly, and pains should be taken to prevent 
any excess getting inside the pipe or couplings. Aquadag contains 
no oil or grease, being a colloidal water and graphite compound 
in which the graphite is permanently suspended in the water. This 
may be used with entire safety and without being over-particular 
about any excess getting inside the pipe. 

The precaution should always be taken when erecting an oxy- 
gen pipe line to blow out each pipe thoroughly, rapping it 
with a hammer to dislodge scale and foreign substances. When 
the line is connected it is also highly desirable to blow it out with 
Compressed air under considerable pressure if possible. Leave 
nothing in the oxygen pipe or manifold of a combustible nature 
whatsoever. A piece of pine wood may take fire, and if fire is 
once started you never know what may happen. 

Welded Pipe Lines 

Permanent installations may be welded with very satisfactory 
results. A welded line will last indefinitely and having no screwed 
joints except at the valves and other connections there is little 
Iiklihood of leaks developing to cause trouble at a critical time. 
Welding is feasible only with iron or uncoated steel pipe. It is 
not advisable to weld galvanized pipe as the welding can be ac- 
complished only with difficulty, and the joints are likely to be 
brittle. When iron or steel coated with zinc are fused the zinr 
is likely to amalgamate with the metal and injure its physical char- 
acteristic. 

Size of Pipe Required for Oxygen Line 

The pipe diameter required for an oxygen line depends of 
course on the length of the line and the number of stations to be 
provided for. A 34-inch pipe will supply all the oxygen needed 
at twenty ordinary stations provided the length of the line does 
not exceed 250 to 300 lineal feet and the total hourly consumption 
d(3es not exceed 500 cubic feet. A steam fitter perhaps will 



Tecommend a larger pipe tlian %-inch for the volume of gas to 
Tdc supplied and would be correct if the line were being erected 
for compressed air used for power purposes. It is necessary then 
to provide a sufficient pipe diameter to prevent considerable drop 
in pressure. But oxygen is a somewhat difficult gas to manage 
and it is advisable to use no larger diameter pipe than experi- 
ence has demonstrated to be sufficient. The comparatively small 




FIG. 1. MANIFOLD AND CONNECTIONS FOP. FOUR OXYGEN CYLINDERS 

pipe recommended will carry all the oxygen required for twenty 
stations and will give less trouble probably than a larger pipe. 
You see that the situation is quite different than with compressed 
air. A compressed air pipe should provide for as little drop in 
pressure as possible but considerable drop in pressure of the 
oxygen supply is of little importance because the source is under 



very high pressure, if furnished in cylinders; an apparatus has 
to be provided to reduce the pressure so that it can be used in 
the torch. The function of a pressure regulator is to reduce 
pressure that is much too high for welding and cutting and to 
maintain an even pressure in the torch. Hence, a comparatively 
small pipe may be safely used to supply a fair sized welding in- 
stallation. The drops to the welding tables should' be ^-inch 
pipe. 

The usual means should be provided for supporting an oxy- 
gen pipe line, and it should be run where it will be out of the 
way and not likely to be struck by heavy objects. Clamps or 
hangers should be provided at regular intervals to support it. 
If the pipe is welded use bent sections for the ells in prefer- 
ence to the commercial ells for two reasons, the first being to 
avoid the use of screwed joints and the second being to avoid 
the disturbing effect of a sharp right angle turn on the flow 
of gas. It is essential in a pipe distributing system that the flow 
be always constant and as free from waves as possible. A small 
pipe of uniform diameter is therefore preferable to a larger pipe 
of uneven diameter and containing many right angle turns. 

Safety Valves for Oxygen Lines 

A simple and reliable safety device should be provided in an 
oxygen pipe line to relieve over pressure in case the pressure 
regulator leaks or fails to function properly. An eflfective de- 
vice consists of a thin brass disc clamped between a flange and 
a cap. The flange is tapped for screw connection to the pipe line 
and the cap is perforated with several holes communicating to 
the atmosphere. The diameter and thickness of the metal disc 
is such that it bursts under a pressure of say 100 pounds per 
square inch and relieves the excess pressure, thus calling atten- 
tion to the defective regulator. 

Acetylene Pipe Lines 

It is necessary to use a somewhat larger pipe for the acety- 
lene supply than for the oxygen because the acetylene pressure 
should never exceed 15 pound's in the pipe lines. A 1-inch pipe 



should furnish all the acetylene required for twenty ordinary 
welding stations and hence a ^-inch oxygen pipe and a 1-inch 
acetylene pipe would be considered to be in about the proper 
ratio for most plant installations that provide gases for hand 
torches only. Gas welding machines, however, may require 
much larger pipe lines, depending on the nature of the in- 
stallation and the number of machines, of course. A circu- 
lar slide, rule is furnished by the Davis-Bournonville Co. for 
calculating the sizes of pipe lines for any installation. 

Gas Manifolds 

When the gases are furnished in considerable volume from' 
cylinders it is usually necessary to provide a manifold for each 
pipe line with pressure reducers to step down the cylinder pres- 
sure before it is admitted to the mains. In a loosely managed 
plant a pressure regulator may be required on each acetylene 
cylinder to control the gas escaping to the manifold. The reason 
for this is that the cylinders containing different pressures are al- 
lowed to be connected to the same manifold. One cylinder may 
contain acetylene under a pressure of say 200 pounds per square 
inch and the one next to it a pressure of only 100 pounds. If 
separate regulators are not provided the result is that the cylinder 
containing gas under 300 pounds pressure discharges abnormally 
fast while the one containing the gas under 100 pounds pressure, 
discharges not at all until the pressure is down to 100 pounds. 
The effect is bad, of course, the object for which more than one 
cylinder is provided being defeated by such practice. 

The need of a pressure regulator for each acetylene cylinder 
connected to the manifold is eliminated simply by connecting cyl- 
inders only to the manifold which contain practically equal pres- 
sures. If four cylinders each containing acetylene under 225 
pounds pressure are connected to the manifold the discharge from 
each should be approximately one-fourth of the total amount of 
gas used hourly or daily. When one cylinder has discharged to 
the lowest pressure permissible to use in the line all of the four 
should also be discharged, and all must be disconnected and re- 
placed by another battery of four. If this practice is faithfully 



followed no trouble need be apprehended from acetone being 
drawn over from one cylinder because of too rapid discharge. 
In order that the discharge of gas should be the same in all 
of a battery of acetylene cylinders it is necessary, however, that 
all should be working under the same conditions. It will not 
do for one cylinder to be set close to a steam radiator in winter 
as its temperature will rise thereby and the rate of discharge will 
exceed that of the others in the cooler zone. Provide as nearly 
as possible the same conditions for all of a battery connected to 
a manifold. 

A manifold is simply a special pipe or header provided with 
as many nipple connections as are required to unite the cylin- 
ders and the pipe line. Flexible coil pipes should be provided 
for the connections between the manifold and the cylinders. The 
oxygen manifold should be made amply strong to withstand a 
pressure of 2,000 pounds to the square inch. The internal bore 
or diameter should be kept to the smallest dimension consistent 
with free flow of gas. A half-inch hole through the manifold 
will be ample for a battery of four or six cylinders. If made 
of a casting it is advisable to use bronze and to make sure that 
it is free of porous spots and pinholes. In some cases stop 
valves are provided at each nipple connection so that the cylin- 
ders may be changed one by one without interrupting the flow 
of gas. If it is necessary to maintain an uninterrupted supply 
of gases, the use of stop valves, of course, is necessary 
but it is practice to be condemned in general because of the 
danger of some of the valves being left closed and all the gas 
being drawn from one cylinder alone. This is not of especial 
moment in the case of the oxygen supply but is a serious matter 
with the acetylene supply. The preferable practice in the case 
of acetylene supply is to provide two manifolds connected to 
the pipe line and to provide no stop valves between the manifold 
and the respective cylinders. This permits a battery of cylinders 
to be kept in reserve ready for instant use, and the discharged 
cylinders may be removed and replaced at leisure. There will 
never be any question about the opening of the stop valves. This 
practice also permits a line regulator to be removed and replaced 
without interruption of service. 



Pressure Regulators 

A pressure reducer or regulator must be installed between 
the manifold and the pipe line. It is not allowable to carry the 
high pressure oxygen in the pipe lines and depend on the station 
regulators to reduce the pressure to the working pressure re- 
quired. Oxygen under a pressure of 1,800 to 2,000 pounds per 
square inch would be much more difficult to keep within bounds 
than if reduced to a line pressure of say 50 pounds. Much bet- 
ter regulation will be obtained also by providing a master regu- 
lator at the manifold and then the drop in pressure to be pro- 
vided for by the individual regulators will be comparatively low. 

Free acetylene compressed to 225 pounds in a pipe line is 
highly dangerous, and is under no circumstances permissible. 
The manifold for the acetylene should be of as few cubic inches 
capacity as possible so as to limit the volume of free gas under 
high pressure as much as practicable. The line pressure to be 
maintained by the master regulator should not exceed 15 pounds 
per square inch. 

Branch Line Pressure Regulators 

If the installation is extensive there being several branch 
lines tapped into the distributing main it may be advisable to 
provide pressure regulators at each branch, especially in oxygen 
pipe lines. Long pipe lines present difficulty in pressure regu- 
lation there being a tendency for surges or waves to be set in 
motion which seriously afifect torch operation. Regulators on 
branch lines will dampen out waves and make the problem of 
individual torch regulation comparatively easy. 

Copper Must Not be Used in Acetylene Lines 

While it is not likely that copper tubing would ever be sug- 
gested for an acetylene pipe line it is, nevertheless, advisable to 
point out the danger of such an installation. Acetylene in con- 
tact with copper forms copper acetylide which is potentially dan- 
gerous, being likely to explode, rupture the pipe and cause a fire. 
The use of brass in acetylene lines should also be discouraged 
but brass stop valves and other fittings are permissible. Gal- 



vanized iron pipe with screw joints or black iron pipe welded or 
screwed together may be used. 

In erecting pipe lines for oxygen and acetylene do not be 
too sparing of stop valves. They should be provided at each 
manifold between the line regulator and the line so that the regu- 
lator may be removed and replaced without discharging the con- 
tents of the line. If the lines are long, stop valves should be 
provided in the mains near each group of welding stations in 
order to save time in case a pipe is ruptured and immediate 
stoppage of gas flow becomes imperative. Stop valves should 
also be placed in the drops to the welding tables in order that 
the regulators may be removed and replaced without interrupting' 
the service. A few dollars invested in stop valves at the vari- 
ous welding stations may save much trouble and inconvenience 
in a busy time. 

Backfire Chamber or Water Seal for Acetylene Lines 

The acetylene line must be protected from the propagation 
of backfires by a backfire chamber of approved design. An ef- 
fective device is one in which the gas bubbles through water in 
passing. The water seals the passage to a backfire and stops 
its propagation. Care must be taken to keep the water replen- 
ished as the effectiveness depends on the water entirely. Back- 
fire chambers should be provided near all junctions of branch lines 
so that each line will have its own protection. 

Generated Acetylene Supply 

So far we have spoken only of the use of acetylene com- 
pressed in cylinders dissolved in acetone. The acetylene supply 
of a manufacturing plant, however, should in general be furn- 
ished by an acetylene generator or a battery of generators. The 
manufacturer using considerable gas can generate his own acety- 
lene much cheaper than he can buy it dissolved in cylinders. 
There will be less likelihood of service interruption because of 
cylinders not arriving on time and the trouble of sending empty 
cylinders back to the supply station will be avoided. Calcium 
carbide may be purchased in large lots in sealed metal containers 
which preserve it indefinitely. Water only is required to convert 

10 



the carbide into acetylene. The cost of maintenance is small and 
the labor charge is inconsiderable. 

The generator house should be located in a remote section 
of the plant away from boilers, furnaces and railway tracks. A 
pit must be provided for discharging the slaked lime residuum. 
It is not generally allowable to discharge the lime into the city 
sewers as it is likely to settle to the bottom and stop them up. 
As the generator house may be a long distance away from the 
welding station it may be necessary then to provide a larger acety- 
lene supply line than recommended in the foregoing. 

Piping Gases to Welding Benches 

A word in regard to the method of piping the gases to the 
welding benches is in order. The pipes may be carried overhead 
and the supply lines dropped to the benches. This form of in- 
stallation is quick and cheap to put in but it has the disad- 
vantage of being unsightly and in some cases it is very ob- 
jectionable. The overhead pipes shut out daylight and tend to 
make the interior of the welding shop unnecessarily gloomy. 
The gas supply pipes should, when feasible, be laid on the floor 
along the wall or under the benches and led up to the welding 
stations from below. There is then nothing in the way above 
the welding bench to interfere with the welder and his work. The 
pressure regulators should be placed where they can be seen 
without effort and controlled without stopping work. 

Questions 

1. Is the use of iron pipe allowable for oxygen pipe lines? 
Why? 

2. What lubricants would you use on the screw threads 
of an oxygen pipe line? 

3. Which would you prefer, a welded pipe line or a screwed 
joint line? 

4. What size oxygen pipe would you use for supplying 
gas to twenty ordinary welding stations, 300 feet from 
the manifold? 

5. What is the purpose of a manifold? 

11 



6. How would you connect an oxygen cylinder to a 
manifold? 

7. Would you use a pressure reducer between each oxygen 
cylinder and the manifold? Why? 

8. Would you put a pressure regulator between the mani- 
fold and pipe line? Why? 

9. Would you put a pressure regulator between the main 
and branch lines ? Why ? 

10. Why would you provide a pressure regulator at each 
station ? 

11. What kind of pipe would you use for an acetylene line? 

12. What size acetylene line would you provide for 20 or 
25 welding stations 300 feet from the generator? 

13. Would you use copper tubing in any part of an acety- 
lene generator ? . 

14. Would you use brass globe valves in an acetylene line? 
.15. Would you use petcocks to drain water from an acety- 
lene line? Why? 

16. What is the maximum pressure to be expected in an 
acetylene line ? 

17. How would. you connect a number of acetylene cylin- 
ders to a manifold? 

18. Would you use pressure reducers for each cylinder? 
Why? 

19. What is the function of a safety valve in an oxygen 
line ? 

20. Is a safety valve needed in an acetylene line? 

21. If a safety valve is not needed what safety device 
should be provided? 



12 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 



THE CUTTING TORCH 
AND ITS USE 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Form 395 



'ACETYLENE 




Davis Bournonvllle Institute 



FIG. 1. THE CUTTING TORCH STARTING A CUT, . AND IN ACTION. 



THE CUTTING TORCH AND ITS USE 

Historical — Iron and Steel are Fuels — Burning Steel Produces High Tem- 
perature — Metals Cut with the Torch — The Modern Cutting Torch — Cutting Tips 
and Gas Pressures — Nicking Billets — The Cutting Torch a General Utility Tool. 

Early in this course of lectures your attention was called to 
the fact that steel will burn in an atmosphere of oxygen. A steel 
or iron wire supported in a jar of oxygen will take fire and burn 
with a shower of sparks when a corner is heated white hot. It 
burns fiercely and is quickly consumed. The products of com- 
bustion are various iron oxides. Steel in an oxygen atmosphere 
will not burn until some part is raised to the igniting temperature. 
The same law holds that applies to ordinary combustion. You 
cannot burn wood without first striking fire with a match and 
igniting the wood or raising a portion to the temperature at which 
it unites with the oxygen in the air. When that has been ac- 
complished, combustion continues until the fuel has been con- 
sumed. The same applies to the steel burning in the oxygen. 
When once combustion has been started the heat produced by 
the burning steel maintains an igniting temperature and com- 
bustion proceeds until all the steel is consumed. 

An atmosphere of oxygen can be produced locally by di- 
recting a jet of oxygen where required. Hence, it is possible to 
produce an oxygen atmosphere in contact with steel or iron with 
a jet issuing from a torch tip and to start combustion or burn- 
ing with a preheating flame. The zone of combustion will be 
confined to the oxygen atmosphere, and that can be fixed by the 
size and direction of the jet. 

Historical 

The possibility of cutting steel and wrought iron with the 
oxy-acetylene torch was discovered in the early years of its de- 
velopment and was recognized as being one of the very valuable 
characteristics of the gas torch. There is no more striking and 
amazing demonstration than the cutting of a steel plate with the 
stream of oxygen issuing from the torch tip. The jet of oxygen 



cuts a narrow, clean kerf like a saw, and the direction of the cut 
can be controlled with such nicety that discs, dies, templets and 
complicated forms may be produced in steel that afterwards re- 
quire little machining in order to make them perfectly true to 
form. 

Altboug'h the chemical effect of oxygen on hot metals was 
well known early in the nineteenth century, the first known refer- 
ence to the use of oxygen for cutting or piercing metal was made 
in 1888 in a paper read by Thomas Fletcher before the Society 
of Chemical Industry in Liverpool, England, in which such ex- 
periments were discovered as "fusing of a hole throug'h a chilled 
iron plate such as those used in burglar-proof safes". Fletcher 
was interested in the manufacture of apparatus using illuminating 
gas and perhaps had the use of illuminating gas in conjunction 
with oxygen in mind. 

A German patent was given to Herman A. E. Menne in May, 
1901, on the use of oxygen for cutting, or as it was termed in 
the patent, "melting" — particularly melting out tap holes in blast 
furnaces which had become solid through cooling. 

A paper read by Chevalier de Schwarz before the meeting 
of the Iron and Steel Institute, in May, 1906, called the atten- 
tion of engineers to the new method of cutting iron and steel 
with oxygen as follows : 

"All experienced blast furnace engineers are acquainted with 
the great trouble caused by tap-holes of blast furnaces becoming 
closed with solid iron so that they cannot be opened up by 
ordinary appliances without considerable loss of time. The usual 
means employed for opening a closed top-hole is a steel bar driven 
by hand rammers, or if these do not suffice, a heavy ram sus- 
pended on chains and worked by a dozen men is employed. It 
sometimes happens that the steel bar snaps off leaving the end 
in the hole already made and making matters worse than they 
were before. Coke and heated blast as well as petroleum have 
been employed for opening closed tap-holes or tuyeres and also 
powerful electric currents, but none of these work quickly enough 
and besides are too expensive, 

"The application of compressed oxygen has worked very 
quickly and has besides the merit of being cheap. The iron to 



be pierced is first heated at the spots selected for making the 
hole by means of an oxy-hydrogen flame. The oxygen and hydro- 
gen are compressed' in separate steel flasks^ each flask being pro- 
vided with a suitable outlet valve. The burner consists of an 
outer and inner tube, the outer tube supplying the hydrogen and 




TRIGGER 
NO. 2018-OXY-AOCTYLENE HAND CUTTING TORCH 




NO. 5000-OXY-ACETYLENE HAND CUTTING TORCH 




NO. 640-OXY-ACETYLENE MACHINE CUTTING TO'OH 




NO. 1314-OXY-ACETYLENE MACHINE CUTTING TORCH 



Davis Bournonvilie Institute 



FIG. 2. STYLES OF DAVIS-BOURNONVILLE CUTTING TORCHES. 

5 



the inner one the oxygen. The hydrogen is turned on first after 
which the oxygen. The pressure of both gases is first kept low 
but is gradually raised and regulated in such a way as to give 
a very hot flame which heats the spot on which it impinges to 
a white heat. The pressure of the oxygen is then increased to 
such an extent that the iron commences to burn, which is shown 
by sparks being thrown out. Thereupon the oxygen pressure 
is increased to 450 pounds per square inch while the supply of 
hydrogen is entirely shut off. It is now that the iron burns, re- 
placing the hydrogen as a combustible, whereupon a degree of 
heat is developed which far surpasses that produced by the oxy- 
hydrogen flame. The high pressure of the escaping oxygen at 
the same time serves to force out all the molten iron thus keeping 
the hole burned through perfectly clean throughout the operation. 
This explains why it is possible to perforate a solid block of cold 
iron or steel say 16 inches thick. Moreover, this extraordinary 
feat can be performed in from one to two minutes." 

The author then proceeded to give an explanation of the 
great increase of heat due to the use of pure oxygen which is 
of interest as it clearly illuminates the extraordinary performance 
of the cutting torch and gives the reader a notion of the power 
of condensed fuel. His words are as follows : "Burning one 
pound of hydrogen with oxygen produces 62,000 B. T. U. while 
burning one pound of iron with oxygen produces 2,968 B. T. U., 
but at atmospheric pressure one pound of hydrogen occupies 
over 80,000 times as much space as one pound of iron. There- 
fore, a certain volumie of iron when burned with oxygen pro- 
duces 4,000 times as much heat as an equal volume of hydrogen 
in the same space. In other words, when iron burns in oxygen, 
the heat is concentrated on a very small area. This explains the 
enormously high temperature produced and the quick action not- 
withstanding that at the same time the temperature of the com- 
pressed oxygen is low because of its compression and subse- 
quent expansion." 

In September, 1906, a United States patent was issued upon 
an application filed in August, 1905, to Felix Jottrand, a Belgian, 
on the process stated to cover a method of cutting plate, pipe 
and other metal articles with a device using a mixture of oxygen 



and hydrogen or other combustible gas together with a jet of 
pure oxygen. There is no direct evidence of the date when 
oxygen was first used for cutting in the United States. The 
claim is made that one Harris of Cleveland cut pieces of steel by 
this method in 1904. Cutting became associated with the in- 
ception of the oxy-acetylene welding process and the early weld- 
ing torches were furnished with a cutting attachment that could 
be clipped to the side of the torch. The oxygen was drawn 
from a separate hose and regulator which required a separate 
cylinder or a double connection to attach two regulators to one 
cylinder thus making a clumsy arrangement. This apparatus was 
more of an interesting curiosity than a practical working tool. 
Upon the development of the cutting torch with only two hose 
connections, the use of the cutting process advanced rapidly, its 
development being made possible by the development of com- 
mercial methods of producing oxygen cheaply and its extensive 
distribution throughout the country compressed in cylinders. 

Metals Cut with the Torch 

The only metals that can be cut with facility with the gas 
cutting torch are wrought iron, mild steels and steels of compara- 
tively low carbon content. High carbon steels are successfully 
cut with the oxygen jet if preheated to a temperature that 
depends somewhat on the carbon content and the various alloys 
contained. The higher the carbon content the greater the degree 
of preheating. A black heat will suffice if ordinary tool steel, 
whereas a low red may be required for some of the alloy tool 
steels. Cast iron cutting is in process of development. True 
cutting of cast iron has not yet reached the commercial stage 
but the progress made within the past year indicates that gray 
cast iron may eventually be cut with as smooth and narrow a 
kerf perhaps as mild steel. At the present time cast iron cutting is a 
combination of cutting and melting. Part of the metal is blown 
away as slag but the greater part is molten iron. Obviously the 
process cannot be thermally efficient until the iron itself burns 
completely and thus contributes the heat required for its own 
combustion. Brass and bronze plates have been cut by inter- 
posing them between steel sheets. The cut produced in the steel 



sheet persists through the brass or bronze plate and the lower 
steel sheet confines the kerf to approximately the same width as 
that in the steel sheet on top. 

The Modem Cutting Torch 

The modern gas cutting torch is similar in appearance to 
the welding torch but differs in the construction and method of 
control. The Davis-Bournonville cutting torch comprises three 
metal gas tubes united in the head and a trigger controlled oxygen 
valve. Two of the gas tubes are for oxygen and the third is 
for acetylene, hydrogen or other combustible gas. The gases re- 
quired for the preheating flame mix in the head of the inter- 
changeable tip the same as in the welding torch. The torch is ap- 
plied for cutting by adjusting the needle valves to produce a 
slightly oxidizing flame. The preheating flame applied to the edge 
of a steel plate quickly raises it to the white hot temperature 
when the trigger controlled oxygen valve is opened thus admit- 
ting streamers or jets of pure oxygen alongside of the preheat- 
ing flame. Instantly the white hot metal takes fire and burns 
with a shower of sparks. The burning (oxidizing) metal rolls 
down the sides of the kerf igniting and burning the metal in its 
path and falling on the floor below. 

The rate of cutting varies with the thickness of the steel, 
the size of tip and oxygen pressure. The No. 1 interchangeable 
tip in the Davis-Bournonville torch requires an acetylene pres- 
sure of three pounds per square inch and an oxygen pressure of 
ten to twenty pounds depending on the thickness of the metal. 
This size tip is suited for cutting steel }i to y\ inch thick. The 
gas consumption, if continuous cutting is about 12 cubic feet 
of acetylene and 55 cubic feet of oxygen per hour on y^ inch 
steel. At the other end of the scale but by no means at the 
limit of heavy cutting, is the No. 5 tip, suited for cutting 10 
inch steel and using 30 cubic feet of acetylene, and 1,000 cubic 
feet of oxygen hourly. The pressure of oxygen required for heavy 
cutting ranges from 100 to 150 pounds per square inch. High 
oxygen pressures are used for very heavy cutting. With high 
pressure the thickness of cutting possible is truly amazing. Armor 
plate 24 inches thick, and even thicker, has been cut successfully 
with the oxy-hydrogen torch. 



Uses for Gas Cutting 

Sufficient has been said to indicate that the uses to which the 
hand operated and machine operated cutting torch can be put to 
in manufacturing, shipbuilding, car building, boiler making, fabri- 
cating and repair work are legend. One of the important uses 
of gas cutting is in the humble junk yard. Old steel boilers can be 
cut with the torch into junk and merchantable plate at small cost. 
For fabrication the cutting torch is invaluable as steel beams, 
angles, channels and other structural shapes may be cut and 
trimmed to any angle required with the torch at a fraction of 
the expense of cutting mechanically. The process is especially 



Acetylene and Oxygen Pressures 

Davis-Bournonville Style C Cutting Torches 

with Style 12 Tips 



Tip 

No. 


Thickness 

of Metal 

Inches 


Acetylene 

Pressure 

Lbs. 


Oxygen 

Pressure 

Lbs. 


Acetylene* 

Consumption 

Per Hour 


Oxygen* 

Consumption 

Per Hour 


1 
1 

1 
1 




3 
3 
3 
3 


10 
15 
20 
20 


12.2 cu. ft. 
12.2 " 
12.2 " 
12.2 " 


42 cu. ft. 

48 " 
55 " 
55 « 


2 
2 
2 
2 


1 


3 
3 
3 
3 


10 
20 
30 
35 


12.2 " 
12.2 " 
12.2 " 
12.2 " 


62 " 

84 " 

106 " 

116 « 


3 
3 
3 
3 


1 

2 
3 


4 
4 
4 
4 


30 
40 
50 
60 

60 

70 

85 

100 


19.7 " 
19.7 « 
19.7 " 
19.7 " 


142 " 
172 « 
202 " 

232 " 


4 
4 
4 
4 


3 

4 
5 
6 


5 
5 
5 
5 

6 
6 
6 

8 


30.6 " 
30.6 " 
30.6 " 
30.6 « 


316 " 
356 " 
416 " 
476 " 


5 
5 

5 

5 


6 

7 

8 

10 


90 
100 
125 
150 


30.6 " 
30.6 " 
30.6 " 
30.6 " 


600 « 

668 " 

838 " 

1,008 " 



Operators frequently adjust the pressure regulators from one to two pounds 
above the figures given in the table to allow for gauge variations and drop of pressure 
when the gases are supplied in cylinders. 

* Gas consumption per hour is the maximum with torch burning continuously. 



valuable in the field where ordinary cutting machines are not 
available. 

This brings up the question of power required for mechanical 
cutting. Steel generally is a high tensile strength metal and can 
be cut apart with tools only by the expenditure of considerable 
power and by the use of expensive cutting tools. The tensile 
strength ranges from 45,000 up to 250,000 pounds per square 
inch, and the power required to separate it by ordinary cutting 
tools is roughly proportional to the tensile strength. It makes 
no difference with the cutting torch, however, provided the carbon 
content is not excessive. The oxygen flame cuts indifferently 
thin and thick metal, treated and untreated without expensive and 
time consuming clamping devices. 

Billet Nicking 

One of the numerous economies effected by the use of the 
cutting torch was developed during the war for cutting bars 
and billets for shells. Such enormous quantities were required 
to be cut to shell lengths that it was impossible to get the ma- 
chines and the operators required for machine cutting. The cut- 
ting torch was used for nicking billets with great success. It 
was found that a billet 5^ inches thick, for example, required 
nicking with the torch flame to a depth only of ^ to % inch. 
The cut cooled by pouring cold water into the kerf immediately 
started a crack which made the breaking of the billet under a 
drop hammer, hydraulic press or on a bulldozer a compara- 
tively easy and quick operation. For cutting 3-inch bars, for in- 
stance, some manufacturers of shells provided nicking tables or 
beds on which several bars 8 or 10 feet long were laid at once and 
guide strips at right angles were provided at regular intervals 
for guiding the nicking torch. The operator nicked the billets 
by passing the torch across the table with the tip held against 
the guide strip. The flame nicked the bars beneath to a depth 
determined by the rate of torch movement. The nick extends 
to a nearly uniform depth through a range of about 120 degrees. 

The nicked bars were broken apart on a bulldozer at 
the rate of about 80 to 100 strokes a minute. 

Some manufacturers of shells adopted other methods among 
which of interest was that of dropping the nicked billets a con- 

10 



siderable distance and letting the shock complete the rupture. 
Three or four billets were raised to a height of 35 or 40 feet 
by means of a lifting magnet and allowed to fall on steel bars 
set so that the nicked billets would strike at or near the nicked 
pieces. As a matter of fact, however, it was found that the 
shock would break a nicked billet in three or four places simul- 
taneously if it struck just right. The production of shell length 
pieces by this method, of course, was very rapid and of low cost. 

The Cutting Torch General Utility-Tool 

The gas welder should use the cutting torch as a tool for 
preparing work for welding wherever it will save time and labor. 
Of course, its use is practically limited to wrought iron and 
steel. But for beveling steel, cutting angles and preparing struc- 
tural parts for assembling and welding, the cutting torch has no 
equal as an efficient tool. Steel plates that require trimming or 
shaping may be cut very quickly and smoothly with the torch. 
If manholes are required it is not necessary even to drill a hole 
as the jet will penetrate and when penetration has been accomp- 
lished the cutting may be directed at will. It is usual to apply 
the jet for penetrating a plate inside the line to be cut out as the 
penetrating jet does not cut as cleanly as it does after penetration 
has been produced. Thus, in cutting out a manhole you should 
lay out the shape and location accurately marking it with chalk 
and then start the cut by penetration inside the line a short 
distance and as soon as the flame has penetrated, work to the 
line and then follow the line closely. 

Questions 

1. Why is it possible to cut wrought iron and steel with 
the torch? 

2. What must be done first in order to start a cut? 

3. What happens if the metal becomes cold? 

4. What gases are used for cutting? 

5. What is the purpose of the trigger-controlled valve in 
the cutting torch ? 

6. What metals can be cut with the torch? 

7. Is it possible to cut cast iron? 

11 



8. What pressure of acetylene should be used for cutting 
a steel plate ^4 ii^ch thick? 

9. To what working pressure of oxygen should the regu- 
lator be set when starting to cut 6-inch steel? 

10. How should the operator hold a cutting torch when 
cutting an arc. 

11. For what purposes is the cutting torch useful? Name 
four. 

12. What should be done after using the cutting torch for 
beveling a steel plate for welding? 

13. What is billet nicking? 

14. Why is it possible to easily break a nicked steel bar? 

15. What should be done by a torch operator before start- 
ing to cut up an old boiler for junk? 



Copyright 1919 by the 
davis-bqurnonvilt,e company 



12 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



Lecture 

GAS CUTTING MACHINES 



DAVIS -BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



GAS CUTTING MACHINES 

Limitations of Hand Cutting — Mechanical Traverse Required as well as 
Mechanical Support — Water Cooling Not Required — Path of the Torch Flame — 
Davis-Bournonville Gas Cutting Machines — The Oxygraph- — Layout for Cutting a 
Steal Die — The Radiagraph — The Pyrograph — The Holograph, Camograph and 
Magnetograph — Comparison with Machine Tools. 

To cut iron and steel smoothly and accurately with a gas 
cutting torch requires considerable manipulative skill, especially 
when the metal is thick. The hand torch operator must hold the 
torch steadily but not firmly', and must follow a line straight 
or curved, as the case may require. The torch movement must 
keep in step with the rate of cutting, progressing no faster or 
slower. If the torch lags behind the cutting action it stops, 
and if the torch moves forward too rapidly the burning away 
of the metal will not keep pace, and the metal will cool so 
that aga:in the cutting action is interrupted. 

Mechanical Traverse Required as well as Mechanical 

Support 

It is important then that any size of tip for cutting a given 
thickness of steel should be traversed at a certain rate ; the 
rate will depend on the pressures of the gases supplied. When 
the gas pressures have been adjusted the effective rate of cutting 
is fixed. The operator must approximate this rate very closely 
in order to prevent interruptions of the work. A machine 
cutting torch, therefore, requires not only a support for the 
torch which will guide and direct its movement but also mechanical 
traverse or feed that can be varied to suit the thickness of the 
metal, the size of tip and other conditions that govern the rate 
of cutting. No cutting torch machine is complete without vari- 
able mechanical traverse, but for small circles and similar cutting 
hand traverse by means of worm gear works very well. 

The Davis-Bournonville Company has developed a number 
of successful gas cutting machines, and a distinguishing feature 



of the larger and most successful machines is mechanical traverse, 
the rate of which may be changed at the operator's will. 

Machine cutting, the same as machine welding is done with 
special torches having the tips in line with the body instead 
of being set at various angles as is necessary in the line of 
hand welding and cutting torches. It is not necessary to pro- 
vide water cooling for cutting torches as the heat affecting the 
torc'h is not nearly as great as with the welding torch, and 
moreover, the volume of oxygen passing through the cutting 
torch is so large that its cooling efifect is considerable. 

Path of the Torch Flame 

The path of the cutting torch through steel is comparable 
to the cut made by a metal saw working under heavy feed. The 
sides are roug'h but regular, nevertheless, within limits. Com- 
paratively little machining is required to finish a flame-cut steel 
block smooth and true. The sides are cut approximately at 
right angles with the top or bottom surfaces. Steel die blocks 
cut to approximate shape with the mechanically-guided and 
mechanically-traversed torch are in condition for finishing to 
size with two or three light machine cuts. The heavy work is 
done by the torch, leaving the accurate finishing work to be done 
on toolroom machines which are better suited for finishing than 
for "hogging" work. The flame can be held close to the line 
when cutting out with confidence that the cut out die will finish 
up smooth and true. The metal is not injured by the flame 
to an appreciable depth, the oxidizing influence being confined 
mostly to the metal cut away. The oxide remaining on the parts 
is very thin and all is removed by the light finishing cuts. 

Davis-Bournonville Gas Cutting Machines 

Machines developed for cutting wrought iron and steel by 
the Davis-Bournonville Company are called the Oxygraph, the 
Radiagraph, the Pyrograph, the Camograph, the Holograph and 
the Magnetograph. Some of these machines are special in their 
characteristics and suited only to special purposes but others are 
more or less universal of application and are, therefore, applicable 
to mac'hine shop and tool room uses and for manufacturing and 
jobbing purposes. 



The Oxygraph 

The Oxygraph is a machine of the pantagraph type, the 
torch being supported on a pantagraph frame that provides for 
horizontal movement in all directions to cover a plane within its 
scope. The pantagraph frame of the No. 1 machine is sup- 
ported at one corner of the frame, and on the opposite end is 
a table on which a drawing may be laid for tracing. The 
torch is mounted on the pantagraph so that the movement is 
reduced to half scale at the torch. Hence, a drawing to be re- 
produced by a cut out pattern in steel with a torch must be 
drawn two times the required size. The lines of the drawing 



o 




n 




LAYOUT, TWICE THE 
SIZE OF DIE 




TRACER WHEEL PATH 



o 



Davis BournonviHe Institute 



FIG. 2. PATTERN DRAWN ON PAPER TWO TIMES SIZE, AND TRACER 
WHEEL PATH FOR OXYGRAPH CUTTING 




Davis BournonviMe Institute 



FIG. 3. PATH CUT BY THE OXYGRAPH TORCH IN A DIE BLOCK 
FOLLOWING PATTERN 



provide allowance for the kerf and finish. These lines are 
are paralleled with lines drawn at such a distance away as will 
mechanically traversed by a motor-driven tracing attachment, the 
speed of which can be varied to suit the thickness of the metal. 

Machine steel plates of any thickness up to 10 inches or more 
may be cut with the oxygraph to any required shape. The torch 
follows straight lines, curves, sharp or obtuse angles, and in fact 
any form that can be laid down on paper and practically cut 
from a steel plate. 

The Oxygraph is made in two sizes, the small size being 
suitable for machine shop and toolroom use while the large 
size machine, which has a double pantagraph frame and two 
cutting torches for making double cuts simultaneously, is es- 
sentially a manufacturing proposition. Drawings laid out for 
cutting on the Oxygraph require the path of the tracer wheel to 







-rfllinll 


^ 




"^ 


< 






^1 


Davis Bournonville 


Institute 



FT3. 4 DIE CUT ON OXYGRAPH, USING PATTERN SHOWN IN FIG 2 

be included in order that the torch path will coincide in re- 
duced scale to the path shaped on the drawing. The tracing 
wheel path should be drawn j\ inch outside of the shape out- 
line when a punch or similar part is to be cut from a steel 
Mock, but if a die is to be cut then the path for the tracer 
wheel should be shown by lines x\ inch inside the shape outline. 

Layout for Cutting a Steel Die 

Fig 2 shows the pattern or drawing for cutting the steel 
die shown in Fig. 4. The outer line is the shape of the re- 
quired opening in the die, and the inner outline is the path of 
the tracer wheel. Fig. 3 shows the die block in reduced scale. 



the ratio being one to two. The torch starts cutting through a 
hole in the center and the path is then directed to the drawn 
hne with the tracer wheel following the path inside. 

As stated in the foregoing, the large size Oxygraph has a 
double pantagraph frame, and is fitted with two cutting torches 
for making two cuts simultaneously. The position of the torches 




FIG. 5. RADIAGRAPH FOR STRAIGHT AND CIRCULAR CUTTING 

and the tracing wheel are adjustable. This machine is suitable for 
cutting several steel parts simultaneously, and is useful where 
many duplicate parts must be cut from mild steel plates. For 
example, take the plate frames of an electric mine locomotive, 
requiring two openings to be cut away for the pedestal jaws in 
which the driving boxes are fitted. The No. 2 Oxygraph is 
admirably suited for work of this character. When put in the 
care of men who have some skill and training, it is capable of a 



large production. The number of parts that can be cut simul- 
taneously depends, of course, on the thickness and the torch 
equipment provided, for example, 12 to 16 plates, % inch thick 
can be readily cut with accuracy when stacked one upon the other. 

The Radiagraph 

The Radiagraph is a motor-driven machine provided with a 
cutting torch and is intended for cutting straig'ht lines or circles 
in steel plates of any thickness up to 18 or 20 inches. The 
speeds of cutting vary from 2 to 10 inches per minute, ac- 
cording to the thickness of the plate, size of tip and the oxygen 
pressures provided. The Radiagraph operates upon a track for 
straight line cutting. The track is made of parallel rails of what- 
ever length required to compass the work. Circular cutting is 
accomplished by the use of a radius arm of adjustable length, 
the torch being carried at the outer end. The carriage is sup- 
ported on three wheels, and is driven by a variable speed elec- 
tric motor which may be used' with either direct or alternating 
current on either 110- or 220-volt circuits. The complete ma- 
chine weighs about fifty pounds and thus is readily portable. It 
is adapted for a wide range of use in shipyards, steel mills, 
forge shops, structural steel plants, fabricating plants, junk yards, 
etc. 

The Pyrograph 

The Pyrograph is a special gas cutting machine designed 
especially for use in boiler shops for trimming flanged boiler 
heads, flue sheets and similar boiler parts. But it is adaptable 
to many other uses in the fabrication of steel parts. The machine 
is similar in general outline to a wall or post radial drill. A 
radial arm supports the torch carriage which is provided with 
a motor for driving the tracing mechanism or friction rollers. 
The torch is adjustable for bevel cutting and the mechanical speed 
fixed according to the thickness of the plate being trimmed, in- 
sures cutting a smooth true bevel. A flanged boiler head, fire- 
box or flue sheet may be accurately trimmed with the machine in 
a fraction of the time required by other methods. The flue sheet 
to be trimmed is blocked up level beneath the swinging arm with 
the flange to be beveled, upward. The cut is started at the 

8^ 



required height with the assurance that tlie flang-e will he trimmed 
to the height required, and that the cut will be maintained 
throughout. The automatic feed provides means for following 
irregular outlines without the guidance of the operator thus 
leaving him free to attend solely to the torch. The machine has 
a cutting area covering a circle of 9 feet diameter at one setting 
and as the traverse on the arm is 10 feet the machine can 
cover a semicircle of 20 feet in diameter when mounted on 
a column. The pivot support, o£ course, can be arranged so 
that the torch may be applied to any part of a circle 30 feet 
diameter. 

The Holograph, Camograph and Magnetograph 

The Holograph is a simple hand-operated machine cutting 
torch for cutting holes in the web of steel rails or steel struc- 




FIG. 6. HOLOGRAPH FOR CUTTING HOLES IN STEEL RAILS AND 
STRUCTURAL SHAPES 



lural parts of not more than % inch thickness. It is so designed 
that the rotating part carrying the torch can be quickly clamped 
in position on the I-beam, channel or rail at the required height 
and position. The torch flame pierces the web without previ- 
ous drilling and smooth, round holes from 1 to 2 inch diameter 
will be cut in from 30 to 60 seconds. The advantages of a 
device of this type for fabricating shops field work, railway and 



bridge work and many purposes required by workers on steel 
structures, tanks and other engineering work are obvious. 

The Camograph is an adaptation of the Holograph having 
the same general form and construction with the addition of a 
cam and mechanism for guiding the torch flame in other than 
circular paths. It was primarily designed for cutting slotted holes 
in street railway rails for the bolts required to hold the fish- 
plates. The precise shape of the hole cut is controlled by the 
shape of the cam provided. Hence, the machine requires special 
cams for each distinct operation. 

The Magnetograph is a radius cutting machine held against 
the parts to be operated on by three electromagnets. The torch 
is mounted on an arm that may be slowly rotated by means of 
•a handwheel operating through a worm and wormwheel. The 
machine was designed especially for cutting holes in armor plate, 
ship plate and for all similar purposes where no easy means 
of : clamping other than magnets are readily available. It cuts 
circles up to 13 inches diameter and steel plate from ^ inch up 
to several inches thickness may be quickly cut with true edges. 
Cutting is accomplished at varying speeds, depending on the 
thickness of plates, the rate varying from 3 inches up to 20 
inches per minute or even faster on thin plates. The holding 
device, consisting of three electromagnets is operated by con- 
necting to any direct-current electric circuit of the required 
voltage. 

Comparison with Machine Tools 

The construction and operation of mechanically-guided cut- 
ting torches is an interesting study for anyone concerned with 
the performance and production in metal working. The ma- 
chine torch operates on a principle so widely different from that 
of the ordinary machine tool that it is somewhat difficult for the 
engineer familiar only with conventional types to appreciate the 
wonderful possibilities of directed combustion of steel. The 
strength of steel is so great that all ordinary machine tools re- 
quire very strong, rigid frames, broad slides, well supported 
cutting tools and powerful drives. The speeds of operation are 
limited by the endurance of the cutting tools and the power 

10 



that can be applied. The cutting torch, however, requires prac- 
tically no power for traversing it, and the supporting mem- 
bers needs only sufficient strength and rigidity to guide the 
torch accurately in its path. The power required to cut the 
steel is supplied by the steel itself through its own combustion. 




FIG. ?. CAMOGRAPH FOR CUTTING SLOTTED HOLES IN STEEL RAILS 

It makes no difference whether the steel has an ultimate tensile 
strength of 50,000 pounds per square inch or 200,000 pounds 
provided the carbon content is not too high. The oxygen jets 
cuts it away smoothly and rapidly. 



Questions 



1. 



5. 
6. 

7. 



Do you understand the principle of the machine cutting 

torch and the hand cutting torch to be the same? 

What distinguishes the machine cutting torch from the 

hand cutting torch? 

Why is a mechanical support desirable for a cutting 

torch ? 

Why is it possible with a machine cutting torch to cut 

a greater thickness than is possible with a hand torch ? 

What is the principle of the oxygraph cutting machine? 

What is first necessary when undertaking to cut a die 

of tool steel with the oxygraph ? 

Is it necessary to drill a hole through steel when starting 

to cut a manhole ? Why ? 

11 



8. What is the Pyrograph cutting machine used' for chiefly? 

9. What is the chief expense in cutting with either the 
hand torch or the machine torch? 

10. For what purpose is the Radiagrap'h cutting machine 
used? 




FIG. 8. MAGNETOGRAPH FOR CUTTING HOLES IN SHIP PLATES AND 
ARMOR. HELD IN POSITION BY MAGNETIC ATTRACTION 

11. Why is a mechanical traverse important feature of the 
torch cutting machine t' 

12. Should the speed of mechanical traverse be fixed or 
variable? 



Copyright 1919 by the 
Davis-Bournonvilt.e Company 



12 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTHUCTION 



Lecture 

CARE OF THE EYES- 
SAFETY CONSIDERATIOISS 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



Copyright 1919 by the 
Davis-Bournonvii,t.e Company 



CARE OF THE EYES- 
SAFETY CONSIDERATIONS 

Protective Colored Glasses — Spectacles and Goggles — General Safety Con- 
siderations — Don'ls for Welders and Cutters. 

Certain clangers and hazards are inherent in almost every 
trade and industry, and oxy-acetylene welding and cutting are 
not exceptions. Gases under pressure are required one of which 
is combustible and explosive when mixed with air or oxygen in 
certain proportions. When gases are furnished compressed in 
cylinders the welder has to deal with heavy pressures of sufifv 
cient intensity to injure his apparatus if not carefully handled. 
The breaking down of a regulator may burst the hose and cause 
injury or a fire. The torch flame is injurious to the eyes unless 
they are protected with suitable colored spectacles or goggles, 
and eye protection must not be neglected when welding or cutting. 

Protective Colored Glasses 

Approved colored glass spectacles or goggles must be worn 
by welders, cutters and their helpers if they would protect their 



FIG. 1. SPECTACLES WITH COLORED GLASSES, SUITABLE FOR LIGHT 
WELDING AND CUTTING. 

eyes from dangerous heat and light rays. The torch flame pro- 
duces light rays of great intensity and also heat rays which may 
be equally destructive to the tissues of the eye. Hardly any 



two men require the same eye protection. But the general rule 
is to provide glasses that shut off no more of the light rays 
than are necessary as the welder may be seriously handicapped 
by being unable to see what he is doing if very dark colored 
glasses are used. There are several tests of the sliitabihty of 
colored glasses, one of which to use a pair of glasses a few 




FIG. 2. LIGHT GOGGLES HAVING COLLAPSIBLE EYE CUPS, HANDY TO 
USE AND CARRY. 



minutes while welding and then remove them and note whether 
white spots dance before the vision. If they are noticeable the 
glasses do not afford sufficient protection and darker ones should 
be provided. Another rough test of the suitability of spectacles 
or goggles is to look through them at vivid red on a blue back- 
ground. Red crayon marks on a blueprint may be tried. If the 
markings may be plainly seen without dazzling effect the glasses 




FIG. 3. VULCANIZED FIBER FRAME GOGGLES, NOT AFFECTED BY HEAT 
OR STERILIZING SOLUTIONS 



may be used. This test, however, is not at all scientific and 
should be used only for want of something better. 

Spectacles and Goggles 

Colored' glasses mounted in steel or aluminum spectacle 
frames as shown in Fig. 1, are suitable for light welding and light 
cutting. They are cheap, convenient and light. Because of the 
open space between the glass and the eyes, sweat is not so 
troublesome as with goggles or other eye protectors that prevent 
free circulation of air. However, spectacles should be worn 
only w'hen there is little danger of flying metal striking the 
face. Spectacles do not afford sufficient protection from flying 
particles in heavy welding and should be worn only for pro- 
tecting the eyes from light and heat. When there are other dan- 




Davis Bournonville Institute 



FIG. 4. GOGGLES WITH QUICKLY DETACHABLE LENSES AND CLEAR 

GLASS COVERS. 



gers to the eyes, goggles or face masks must be worn if the 
welder would be safe. 

Goggles are made in a variety of forms, and the choice of 
goggle is largely a matter of individual preference and the amount 
that one would be likely to invest. The goggles shown in Fig. 2 
are light and the lenses are easily replaced in case of breakage. 
The mask is of unlined leather and an elastic head band is pro- 
vided. The eye cups being collapsible the goggle can be carried 
in the vest pocket without a case. Cases, however, should be 
provided to protect the glasses from dust and abrasion. The 
goggles shown in Fig. 3 have frames of vulcanized fiber, light 



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FIG. 5. BICOLOR GOGGLES, USEFUL FOR GENERAL REPAIR WELDING. 

in weight and a good non-conductor of heat. The fiber is non- 
inflammable and infusible, and is not affected by moisture. Con- 
sequently, the goggles can be sterilized without injury, which is 
an important consideration where several welders are employed 
and the goggles are common property. The eye cups are con- 
nected with a rubber covered chain. An elastic head band is 
provided to hold the goggles in place. The colored' lenses are pro- 
tected by clear glass lenses which may be readily replaced when 
pitted by flying globules of molten metal. This is an important 
consideration when purchasing goggles. Unless the colored glass 
is protected it will soon be so pitted in use as to become useless 





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FIG. 6. SPECTACLES WITH VENTILATED SIDE SHIELDS. 

6 



It is cheaper to replace the clear glass protectors than the more 
expensive colored lens. 

The eye cups of the goggles shown in Fig. 4 are made of 
aluminum, bound at the edges to prevent contact with the face. 
The distance between the lenses may be changed by twisting the 
connecting chain. The colored lenses are protected by clear cover 
glasses which may be readily replaced when injured by pitting. 
No tools are required to replace a lens, all that is required 
being to twist the rim slightly to one side and remove the les 
by pressure with a finger applied from the inside of the eye cup. 

The bi-color goggles shown in Fig. 5 are provided for welders 
who wish to inspect their work without the trouble of removing 




FIG. 7. GOGGLES WITH VENTILATED EYE CUPS AND SIDE SHIELDS. 

colored glasses from the eyes. The lower part being colored 
glass and the upper part clear glass, the operator may see "day- 
light" through his goggles without removing them. The eye 
cups are flexible, ventilated leather, and spectacle bows are used 
instead of an elastic head band. 

Spectacles with ventilated side shields and metal frames are 
shown in Fig. 6 and goggles with ventilated eye cups and ven- 
tilated side shields in Fig. 7. These fornis are recommended 
for oxy-acetylene welders by the Bureau of Standards but, as 
stated in the foregoing, the choice of goggles is largely a matter 
of individual preference. A protective goggle may be everything 
that could be desired from the protective standpoint but if it in- 
duces excessive perspiration or is heavy and inconvenient it will 



be hard to induce men to wear them. A case in point is the 
face mask shown in Fig. 8 which undoubtedly is effective pro- 
tection. It has the advantage that the mask may be quickly raised 
from the eyes to permit the welder to inspect the work but the 
head band is more or less uncomfortable and the mask is likely 
to induce profuse sweating. Some men, however, find this type 
of eye protection agreeable and satisfactory. 

General Safety Considerations 

Welders and cutters should wear suitable clothing. A long 
apron over street clothes or overalls free from holes or rags are 
generally satisfactory. Attention should be given to the shoes 




OPERATIVE 



INOPERATIVE 

Davis Bournonville Institute 



FIG. 8. FACE MASK MOUNTED ON HEAD BAND SO THAT IT CAN BE 
MADE OPERATIVE OR INOPERATIVE WITHOUT REMOVING. 

as broken shoes are dangerous on account of the possibility of 
drops of molten metal falling into the holes and seriously burn- 
ing the feet. Gloves should be worn to protect the hands from 
the heat of the torch flame, but avoid cheap cotton gloves that 
catch fire. Wear leather gloves or fabric gloves that have been 
treated to make them fireproof. 

Care must be taken when setting up work for welding that 
it cannot be easily displaced and fall to the floor while welding. 
The result of such an accident may mean serious injury either 



from contusions or burns. When welding preheated castings 
care should be taken of the hose to prevent it coming into con- 
tact with the hot metal and being burned, and in general, good 
care should be taken of the hose to prevent cutting and burning. 
Hose at best is short-lived and it should be well cared' for in 
order to get the most use out of it possible and to prevent burst- 
ing in use. Bursting of the hose under a pressure of even a 
few pounds is startling if not worse. 




FIG. 9. SAFETY PRESSURE GAUGfi. BACK IS HINGED SO THAT IT 

RELIEVES PRESSURE IN CASE OF FAILURE WITHOUT 

BLOWING TO PIECES. 

Never neglect a leaky joint. If the odor of acetylene is 
strong find the leak and stop it. A leak is not only costly but 
dangerous and should never be tolerated under any circumstances 
whatsoever. 

If acetylene is generated on the premises it should be put 
in the care of an intelligent careful man who should be instructed 



how to charge and recharge according to directions. The genera- 
tor house should be kept locked and should be located away from 
boilers, furnaces and flying sparks from passing locomotives. 

Cylinders containing acetylene and oxygen should never be 
exposed to the heat of furnaces nor should they be left standing 
in the sun on hot summer days without protection. The heat 
may expand the gases and increase the pressure to a dangerous 
point and even if no accident results the safety plugs may blow 
and waste the gases. 

Fire protection should be provided in the welding shop either 
in the form of fire pails, chemical extinguishers, or sprinkler 
heads. A portable extinguisher is an important part of the gen- 
eral equipment and it is advisable to take one along when going 
out on a field job. An extinguisher will serve to put out a small 
fire which if it gains headway may result in a serious disaster. 

The skill of an oxy-acetylene welder and the conscientious- 
ness with which he does his work are important safety factors. 
A poorly welded job may fail and cause loss of life or limb and 
the destruction of property. The welder should therefore have 
constantly in mind the things he should and should not do for 
the safety of himself and apparatus, and also to insure dependable 
work that will not imperil others when in use. 

Dont's for Welders and Cutters 

Don't connect a regulator to a cylinder without cleaning off 
the joints. 

Don't open a cylinder stop valve quickly. 

Don't open a cylinder stop valve part way; open it as far 
as it will go. 

Don't connect the hose to the torch without blowing out. 

Don't open a cylinder stop valve without making sure that 
the regulator handle is released. 

Don't open a regulator valve quickly ; turn the handle slightly 
at first and give the diaphragm a chance to operate. 

Don't stand close to the regulator when opening the cylinder 
valve. 

Don't use a defective pressure gauge. 

10 



Don't use oil or grease on any oxygen connection that comes 
in contact with the gas. 

Don't leave a welding outfit with the gas turned on; always 
shut the cylinder valves when leaving. 

Don't try to adjust the regulator with the torch needle valves 
closed. 

Don't neglect to put in the right size tip when starting to weld. 

Don't neglect to adjust the regulator so that the working 
pressure is correct for the thickness of metal to be welded. 

Don't stand behind an oxygen high pressure gauge when 
opening the cylinder valve. 





MUSCULAR 
TRAINING 


WELDING 
SKILL 


PRACTICAL 
WORK 


EXPERIENCE 






CISES >. 








-I 

03 




^^ 


/^ POINT 


AT WHICH SELF CONFIDENCE 
IS REGAINED 


ill 

> 




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DROP IN MANIP 
TO LOSS OF S 


JLATIVE SKILL DUE 
ELF CONFIDENCE 


»- 




/ 


CAUSED BY CHANGED CONDITIONS | 


-1 
3 
0. 

z 
< 




/ COURSE OF INSTRUCTION > 

^ POINT AT WHICH SUBCONSCIOUS MANIPULATION STARTS 




1st WEEK 


2nd WEEK 


3rcl WEEK 


INDEFINITELY | 



Davis Bournonville Institute 

FIG. 10. CHART ILLUSTRATING PROGRESS OF WELDERS WHEN LEARN- 
ING. ACCIDENTS LIKELY TO HAPPEN IN THIRD WEEK. 

Don't use a regulator with a leaky valve. 

Don't use matches to light the torch; use a flint ignitor. 

Don't use a porous or leaky hose. 

Don't let oil drip on the hose. 

Don't let the hose become overheated from close contact with 
a preheated casting. 

Don't let flashbacks burn in the head ; close the oxygen valve 
at once. 

Don't turn on the acetylene cylinder valve first in starting 
to weld. 

Don't open the oxygen needle valve first when lighting the 
torch. 

Don't fail to wear goggles to protect the eyes. 



11 



Don't wear ragged clothes likely to catch fire when welding 
or cutting. 

Don't fail to wear an apron or overalls. 

Don't wear broken shoes in a welding shop. 

Don't neglect the torch ; hang it up when through welding. 

Don't use the torch head as a, hammer. 

Don't let the tip drop into the puddle. 

Don't let the tip of the white hot cone touch the molten metal. 

Don't fail to give the torch a semicircular zig-zag motion on 
prepared joints. 

Don't use ordinary iron or steel wire for adding material. 

Don't use common cast iron welding sticks. 

Don't try to make your own fluxes. ; 

Don't waste flux. 

Don't let tips lie around on the welding table ; keep them cov- 
ered in a box. 

Don't try to remove the head of a torch from the tubes. 

Don't fail to clamp the hose firmly to the nipples. 

Don't lay an acetylene cylinder down flat on its sides. 

Don't use acetylene too fast from a cylinder. 

Don't neglect the odor of acetone when welding; you are 
using the acetylene too fast. 

Don't leave gases under considerable pressure in cylinders; 
use as much as you can before returning an "empty". 

Don't neglect to put the cylinder cap over the cylinder when 
returning it to the manufacturer. 

Don't move cylinders about the plant with the regulators in 
place ; always take them ofif. 

Don't pull on the regulator with the hose. 

Don't let an acetylene or oxygen cylinder stand near a fur- 
nace or boiler. 

Don't let an acetylene or oxygen cylinder stand out in the 
hot sun when fully charged without protection. 

Don't handle gas cylinders roughly either when filled or 
empty. 

Don't let an oxygen cylinder stand beneath a dripping line- 
shaft. 

Don't let an oxygen cylinder get oily or greasy. 

12 



Don't let acids drip on gas cylinders. 

Don't test a pressure valve with oil; use water or glycerine. 

Don't melt the welding rod with the torch flame. 

Don't neglect to break down the sides of the vee when 
welding. 

Don't forget that the puddle must melt the adding material. 

Don't use a -^jr inch welding wire on a ^ inch weld. 

Don't use square or twisted wire adding material. 

Don't let adding material get rusty. 

Don't fail to bevel the edges when preparing to weld. 

Don't overheat brass or bronze when welding or brazing. 

Don't try to weld a broken malleable iron casting ; braze it 
instead. 

Don't forget that a brazed joint is very strong and often 
preferred to a welded joint. 

Don't forget to support aluminum under the weld. 

Don't try to weld aluminum without using a puddling stick. 

Don't forget that aluminum can be welded smoothly with 
flux. 

Don't overheat an aluminum casting. 

Don't use the torch flame for preheating ; it is too expensive. 

Don't forget that high carbon steel melts at lower tempera- 
ture than low carbon steel, and is easily burned. 

Don't forget that cast iron melts at a lower temperature than 
steel and that it requires scaling powder. 

Don't go into an acetylene generator house with a lighted 
pipe, cigar or cigarette. 

Don't neglect to remove all the residuum when recharging 
an acetylene generator. 

Don't neglect a leaky pipe joint in an acetylene line. 

Don't force carbide into the opening of a generator with 
a metal rod ; a spark might be struck that would ignite the gas. 

Don't forget to blow off the acetylene and air mixture in a 
generator when first starting. 

Don't undertake to weld or solder an acetylene generator 
shell without filling it with water to force out all gas. 

Don't do any welding or soldering on an acetylene generator 
if there are other generators in the same room. Remove the 

13 



generator before making the repair. 

Don't let an acetylene generator run on a pressure of more 
than 15 pounds per square inch. 

Don't forget to keep the backfire or flashback chamber filled 
with water to the level of the overflow plug. 

Don't let any foreign substances go into the hopper of an 
acetylene generator with the carbide. 

Questions 

1. Why should you be careful in handling an oxy-acetylene 
welding outfit ? 

3. What is the pressure in an oxygen cylinder when re- 
ceived from the manufacturer? 

3. How does the pressure in an oxygen cylinder compare 
with the pressure in a steam boiler? 

4. What might be the effect on an oxygen or acetylene 
cylinder if set close to a furnace or if left out in the 
sun on hot days? 

5. How is acetylene stored in an acetylene cylinder? 

6. What happens if the acetylene is drawn off too rapidly? 

7. How can you tell when gas is being drawn too rapidly 
from an acetylene cylinder? 

8. How should one proceed to find a gas leak in an acety- 
lene pipe? 

9. Why should a welder wear colored glasses? 

10. When may spectacles with colored glasses be worn ? 
When should goggles be worn? 

11. How would you determine whether a pair of goggles 
were suitable for your eyes? 

12. What causes pitting of colored glasses? 

13. Did you ever see colored spectacle glasses pitted on the 
inside? How could that be possible? W^hat does it 
show ? 

14. What precaution should be taken with all goggles when 
used by a number of welders? 

15. What provision is made to prevent the expensive colored 
glass in goggles becoming pitted? 

14 



16. What kind of shoes is safest in a welding shop, foun- 
dry or other place where molten metal is liable to fall 
on the feet? 

17. What should be done when the flame flashes back in 
the torch? 

18. What precaution should be taken with hose? 



15 



i 



DAVIS-BOURNONVILLE 

OXY-ACETYLENE WELDING and CUTTING 

COURSE OF INSTRUCTION 



GLOSSARY 

Terms used in Oxy-Acetylene Welding 
and Cutting 



DAVIS-BOURNONVILLE INSTITUTE 

JERSEY CITY, N. J. 



COPYRldHT 1919 BY THB; 

Davis-BournonviIvLE Company 



GLOSSARY 

Definitions of terms and words used in oxy-acetylene welding and cutting, together 
with chemical names and formulas. 

Acetone. (CgHgO) An inflammable liquid of distinctive 
odor and biting taste made by the destructive distillation of 
wood. It has remarkable solvent power for acetylene gas, the 
absorptive capacity being 24 to 25 volumes acetylene per 
volume of liquid per atmosphere. Used as the solvent liquid 
in acetylene cylinders. 

Acetylene. (CoHo) A combustible gas of high thermal 
value made by slaking calcium carbide with water, and used 
for welding, cutting, lighting and cooking. 

Acid Sodium Carbonate (NaHCOg) Bicarbonate of soda 
or common baking soda (saleratus). 

Adapter. A screw fitting for coupling pressure regulators 
to cylinders and provided with right or left hand threads, or 
both, of various diameters to fit. 

Adding Material. The filler rod used in welding. Also 
called welding rod or welding wire. 

Adhesion. Condition in a weld resulting from imperfect 
union and little penetration, comparable to a glued or cemented 
joint. 

Agitator. The revolving paddle of an acetylene generator 
for stirring up the residuum before discharging it to the sewer. 

Alignment. The state of being in line or in the original 
relation. A broken curved casting is in alignment when the 
parts are placed in the original relation. 

Alloy. A homogenous mixture of two or more metals. 

Ammonia. (NH^OH) Spirits of hartshorn, the aqueous 
solution of gaseous ammonia, NHg. 

Ammonium Chloride. (NHj^Cl) Sal-ammoniac. 

Angle Bar. A rolled steel bar the cross section of which 
is usually an angle of 90 degrees. 

Anode. The negative electrode of an electrolytic gener- 
ator on which the hydrogen gas collects. 



Aqua Regia. A mixture of nitric and hydrochloric acids 
in the proportion of 1 part nitric acid to 3 parts hydrochloric. 
Used for dissolving gold and for etching metals. 

Asbestos. A mineral substance composed mainly of 
magnesium silicate, which is spun, woven or felted and having 
high heat-resisting and insulating qualities. Used for pro- 
tecting work when preheating and after welding. 

Asbestos Blanket. The woven absestos fabric of an elec- 
trolytic generator to separate the gases. 

Atmosphere. The pressure of the air at sea level, 14.7 
pounds per square inch. A pressure of 10 atmospheres is 147 
pounds per square inch. 

Autogenous. Self-produced, and as applied to welding, 
meaning the welding of metals by fusing without the use of 
additional metal and without hammering. The term is loosely 
applied to all gas welding with or without the use of adding 
material. 

Babbitt. An anti-friction nietal used for lining bearings. 
The original babbitt formula is said to be about 50 parts tin, 
2 parts copper and 4 parts antimony. 

Backfire. Penetration of a flashback through the torch 
into the handle, hose or pressure regulator. A backfire is 
caused by firing an accumulation of mixed gases, due generally 
to faulty manipulation of the cylinder stop valves, improper 
regulator adjustment, incorrect procedure in turning on and 
lighting the gas, or dipping the tip into the molten metal. See 
Flashback. 

Bearings. The support or wearing surface in a box or 
a revolving shaft. See Journal. 

Bell. A receiver for storing gases, consisting of an in- 
verted metal cup floating in water and water sealed at the 
mouth. 

Bevel. An angle of other than 90 degrees formed on the 
margin of a plate or casting when prepared for welding. 

Blowhole. A hole or cavity in metal formed by gas. 

Blow-off Valve. Hand operated safety valve of an acety- 
lene generator to clear the chamber of air and acetylene mix- 
ture after charging. 



Blowpipe. Originally a straight or curved pipe used by- 
workers of precious metals for ^blowing' an alcohol flame 
against the parts to be melted or soldered. A gas burner in 
which the combustible gas and air or oxygen are mixed and 
burned to produce a high temperature fliame. The term 
"torch" is given the preference in America when applied to 
the oxy-acetylene apparatus for welding and cutting. 

Bourdon Tube. The flattened curved tube of a pressure 
gauge which tends to straighten under internal pressure. 

Bottle. A pressure container for transporting acetylene, 
oxygen, hydrogen or other gas. See Tank or Cylinder. 

Brazing. A process of uniting metals by heating with a 
brass or bronze alloy of low fusing temperature. Also called 
hard soldering. 

Burning. Applied to lead, meaning the process of joining 
lead sheets for acid tanks by autogenous welding. 

Burning on. The process of replacing part of a broken 
casting in the foundry by pouring molten iron through a sand 
mold containing the casting until it is preheated and fused 
along the margins of the broken parts when the pouring is 
stopped and the metal permitted to cool and unite. 

Butt Joint. A seam made by butting two edges together. 

By-pass. Passage in the cutting torch connecting the 
oxygen supply with the preheating oxygen tube. 

Calcium Carbide. (CaCo) Material used for the produc- 
tion of acetylene gas by slaking with water. 

Calcium Chloride. (CaOClo) Chloride of lime. Bleach- 
ing powder. 

Calcium Hydroxide. (Ca(OH)2) Slaked lime. 

Calcium Oxide. (CaO) Quick lime. 

Camograph. A hand-operated torch cutting machine for 
cutting slotted holes in rails. 

Cap. The metal protector screwed over a cylinder stop 
valve to prevent injury in transit. 

Carbide Filling Plug. The screw plug in the top of an 
acetylene generator which is removed when filling the hopper. 

Carbon Dioxide. (CO2) A product of perfect combus- 
tion of carbon, a heavy colorless incombustible gas. 



Carbonite. Carbon compressed into rods and sheets used 
as a fire resisting dam in building bosses, lugs, gear teeth and 
other parts. Also called carbon blocks. 

Carbonizing. Having the quality of imparting carbon 
and meaning, when applied to the torch flame, an excess of 
combustible gas which deposits carbon in the molten metal. 
See Carburizing. 

Carbon Monoxide. (CO) Product of imperfect combus- 
tion. 

Carburizing. Same 'as carbonizing, but preferable 'for 
carbon imparting. 

Casehardening. The process of carburizing the surface 
layers of mild steel and raising the carbon content to the point 
where the steel will harden when heated to a cherry red and 
dipped in water. 

Cathode. The positive electrode of an electrolytic gener- 
ator on which the oxygen gas collects. 

Cell. An electrolytic generator unit. 

Channel. Structural shape having flanges turned on each 
side forming a trough. 

Chipping. Removing metal with a hammer and chisel. 

Coefficient. The factor used to determine the expansion 
of metals by heat. Generally expressed per one degree change 
of temperature F. The coefficient of expansion of steel is 
0.00000636. 

Cohesion. Condition resulting from perfect fusion and 
penetratioji which locks the molecules of parent metal and 
adding material together. 

Column. A vertical support made of structural steel or 
cast iron. 

Combustible. Anything that burns in the air or an atmos- 
phere of oxygen. Same as Inflammable. 

Compressor. A water cooled gas pump for compressing 
oxygen, hydrogen, or acetylene into cylinders. 

Connector. A fitting for joining lengths of hose. 

Content. The quantity of a material contained in a metal,, 
such as the carbon, nickel or titanium content of steel. 

Contraction. The shrinkage of metal in cooling. 



Copper Sulphate. (CUSO4) Bluestone or blue vitriol. 

Countersink. To bevel the edge of a hole to fit the 
tapered head of a bolt or rivet. 

Coupling. A threaded sleeve for joining pipes. 

Conical Seat. The joint in the torch head fitting the inter- 
changeable tip. 

Creeping. The building up of pressure in a pressure regu- 
lator when not in use. Caused by gas leaking through the 
regulating valve. 

Cross Bar, The handle of the regulating screw of a gas 
pressure reducer or regulator. 

Cutting. The term applied to the burning of wrought 
iron, steel, and cast iron with a jet of oxygen. 

Cutting Torch. A torch or blowpipe with one or more 
heating jets and an oxygen jet, used for cutting iron and steel. 

Cylinder. A pressure container for holding gas under 
pressure. Also called Tank and Bottle. 

Cylinder Filler. The porous contents of an acetylene 
cylinder made of asbestos, charcoal, infusorial earth and 
cement, compacted to completely fill and leave no open space 
for the collection of free acetylene gas under pressure. 

Cylinder Valve. The outlet stop valve of a gas cylinder. 

Dial. The graduated face of a pressure gauge. 

Diaphragm. The flexible partition in a regulator beneath 
the regulator spring. Also the partition in a high pressure 
gauge to protect the glass from being blown out when the 
Bourdon tube bursts. 

Dissociation. Separation attended by the release of heat 
such as develops intensely in the combustion of acetylene with 
oxygen in the torch and produces the white hot cone having a 
temperature of about 6300 degrees F. Dissociation of acety- 
lene may result from over-pressure and shock. 

Drift. A tapered hand punch for enlarging and lining up 
rivet holes in plates. 

Ductile. That which can be drawn or stretched. 

Ductility. The property of iron, steel, copper, brass and 
other metals which permits them to be drawn into wire. 

Duograph. A motor driven torch welding machine for 



welding cylinders, containers, steel barrels, etc. 

Elastic Limit. The maximum load sustained by a test bar 
just before it begins to stretch. 

Electrode. Either of the poles of an electrolytic cell. 
Oxygen is liberated on the positive electrode and hydrogen on 
the negative electrode. 

Electrolyte. The water and caustic soda solution in an 
oxygen and hydrogen electrolytic generator. 

Elongation. The stretch of a bar when pulled apart in a 
testing" machine. Genearally ex;pressed in [percentage of a 
definite length of the specimen. 

Endothermic. Pertaining to the absorption of heat. 
Acetylene gas is an endothermic substance, heat being ab- 
sorbed in the reaction of calcium carbide and water by which 
it is produced. Few chemical compounds are endothermic. 

Etching. Corroding a polished metal surface with acid or 
other chemical to show the physical structure. 

Exothermic. Pertaining to compounds whose formation 
is attended with development of heat, and whose dissociation 
absorbs heat. Most chemical compounds are exothermic. 

Expansion. The increase in length, breadth and thick- 
ness of metals due to heat. 

Feeding Disc. Revolving plate on which the carbide 
drops from the hopper of an acetylene generator when feeding. 

Filler Rod. The adding material or welding rod used to 
fill a welded joint. Also called Adding Material and Welding 
Rod. 

Fillet. The material used to fill a corner and to round the 
angle. 

Filter. An apparatus for removing dust and floating im- 
purities from acetylene gas. 

Flame. The combustion of gas. 

Flashback. Snapping out of the flame and penetration of 
the flame into the torch mixing chamber but no further. A 
flashback is generally caused by an obstruction in the tip or by 
overheating of the tip and head. See Backfire. 

Flux. Any material used to dissolve oxides, to release 
trapped gases and slag and to clean metals for welding and 



soldering. 

Fracture. A break. Applied to broken metal surfaces. 

Fuse. To melt. 

Fusing. Melting (with heat). 

Gas. The form of matter usually invisible which may be 
indefinitely compressed and expanded, having no coherence or 
form, such as acetylene, oxygen, hydrogen, nitrogen, chlorine,, 
etc. 

Gasometer. A bell or receiver for storing gases. See 
Bell. 

Gauge. An instrument usually having a circular gradu- 
ated dial and movable hand for measuring pressures of gases 
in pressure containers. 

Generator. An apparatus for producing gas and usually 
applied to the means for producing acetylene or oxygen. 

Girder. A beam of I section built of plates and angles. 

Goggles. Colored glasses for protecting the eyes from 
destructive heat and light rays. 

Grain. The arrangement of the large crystals visible in a 
metal fracture. 

Handle. The part of the torch held in the hand. 

Handwheel. Any disc or wheel handle of a valve or other 
apparatus. 

Holograph. A hand operated torch cutting machine for 
cutting holes in the webs of rails and structural steel. 

Hopper. The receiver for calcium carbide in an acetylene 
generator. 

Horizontal. Level or parallel with the horizon. Applied 
to welding in a level position. 

Hose. Flexible rubber pipe reinforced with fabric. Used 
to connect the torch with the sources of gas supply. 

Hydrochloric Acid. (HCl) Muriatic acid. 

Hydrogen. (H) A colorless, odorless, combustible gas, 
the lightest known. Used for welding and cutting. 

I-Beam. A structural shape having a cross section like 
the letter I. 

Inflammable. That which can be burned. Same as Com- 
bustible. 



Interchangeable. That which can be interchanged, like 
the tips of Davis-Bournonville cutting and welding torches. 

Jet. The stream of gas issuing from a torch tip. 

Journal. The wearing surface of a revolving shaft in a 
bearing. See Bearing. 

Kerf. The fissure made in iron or steel by the cutting 
torch. 

Key. The handle used to open and close a cylinder stop 
valve. 

Laminated. Composed of sheets in layers. 

Lead Carbonate. (PbCOg) White lead. 

Lead Oxide. (PbO) Litharge. 

Line. A metal pipe or rubber hose for gas. 

Liquefaction. Reducing a gas to the liquid state by com- 
pression and refrigeration. 

Magnetograph. A hand operated torch cutting machine 
for cutting holes in ship plates, provided with magnets to hold 
the machine in place. 

Main. The principal distributing pipe of a gas line 
system. 

Malleable. That which can be shaped by hammering, 
bending or drawing. 

Manifold. A metal header or multiple connection for con- 
necting several gas cylinders to a pipe line. 

Mercury. (Hg) Quicksilver. 

Mild. Applied to steel to indicate low carbon content and 
characteristics similar to wrought iron. 

Mixing Chamber. That part of the torch in which the 
combustible gas and oxygen are brought together. 

Monel, A natural alloy of copper and nickel. 

Motor. Weight or spring-driven clockwork mechanism 
for revolving the feeding disc of an acetylene generator. 

Muriatic Acid. (HCl) Hydrochloric acid. 

Needle Valve. A small valve with a conical seat capable 
of fine adjustment and used in cutting and welding torches for 
regulating the gas mixture. 

Neutral. Applied to flame meaning neither carbonizing 
nor oxidizing. 

10 



Nipple. A short piece of screwed pipe. 

Nitric Acid. (HNO3) Aqua fortis. 

Nozzle. The discharge part of an apparatus. Sometimes 
applied to the tip of a torch. 

Overhead. Applied to joints in a ceiling or overhead. 

Oxide. Combination of oxygen with metal generally in 
the form of rust, corrosion, coating, film or scale. 

Oxidization. Combining with oxygen and forming an 
oxide. 

Oxidizing. Applied to the torch flame meaning a flame 
containing an excess of oxygen gas which burns the molten 
metal. 

Oxygen. The supporter of combustion comprising about 
one-fifth the atmosphere. Furnished commercially pure, com- 
pressed in cylinders to a pressure of 1800 to 2000 pounds pres- 
sure per square inch for torch welding and cutting. 

Oxygraph. A machine cutting torch mounted on a panta- 
graph reducing gear with a motor driven tracing wheel, so 
designed that a drawing can be traced and reproduced in the 
part cut out with the torch. 

Parent. The metal welded. Used to distinguish the parts 
welded from the adding material or welding rod. 

Peening. Stretching cold metal by striking with the peen 
of a hammer. 

Penetration. Welding clear through' the joint. Indicated 
by the molten metal appearing in drops or globules on the far 
side. 

Pet-cock. A small discharge valve with a plug or key re- 
quiring a 90-degree turn to open or close. 

Photomicrograph. Photograph of microscope enlarge- 
ment of a metal specimen. 

Plumb-bob. A weight with conical tip suspended with 
string to show the vertical line. 

Pole. One of the two terminals of an electrolytic genera- 
tor, know as positive and negative. 

Polymer. Product of high temperature generation in an 
acetylene generator. 

Polymerization. The effect of high temperature in acety- 

11 



lene generators which is shown by the presence of yellow tarry 
deposits. 

Pool. The small body of molten metal formed by the 
torch flame. Also called Puddle. 

Potassium Carbonate, (KgCOg) Potash. 

Potassium Chlorate. (KCIO3) Chlorate of potash. 

Preheating. Heating metal plates or castings previous to 
welding in order to minimize expansion and contraction 
stresses and to save gas. 

Pressure. The force exerted by a confined gas or liquid. 
Measured in pounds per square inch. 

Pressure Reducer. An apparatus for reducing and regu- 
lating the pressure of gases used for welding and cutting. 

Pressure Regulator. An apparatus for maintaining a 
nearly constant pressure of the gases used for welding and 
cutting. All pressure regulators are reducing valves, and 
operate by lowering the pressure of gas supplied from 
cylinders, generators or pipe line systems to the working pres- 
sure required. 

Puddle. The fused body of metal directly beneath the 
torch flame. Also called the Pool. 

Puddle Stick. A steel rod flattened at the end and formed 
in various shapes for breaking up oxides and removing slag. 
Used especially in welding cast aluminum without flux. 

Puddling. The breaking up of oxide and elimination of 
slag and oxide from the puddle, especially when welding cast 
aluminum without flux. 

Purifier. An apparatus for removing sulphurreted hydro- 
gen and other gases from acetylene. 

Pyrograph. A torch cutting machine for beveling and 
trimming flanged boiler heads and boiler plates. 

Radiagraph. A motor driven torch cutting machine for 
cutting straight lines or circles in steel and iron plate. 

Reaction. The change resulting from a chemical combi- 
nation or a mechanical action. 

Reducing. Applied to flame, meaning carbonizing or 
carburizing, the opposite of oxidizing. 

Regulator Screw. The part of a pressure regulator by 

12 



which the tension of the diaphragm spring is adjusted. 

Residuum. The shidge or accumulation of water and 
slaked lime in the bottom of an acetylene generator. 

Ribbon Flame. The torch flame produced with a tip 
having a narrow slot orifice. 

Ripple. A general characteristic of steel welds made with 
the hand torch, similar in appearance to the surface of water 
under an air current. 

Safety Disc. A sheet brass disc in combination with a 
fusible alloy designed to blow out under excessive pressure or 
heat or both. 

Safety Valve. A fitting connected to a gas pipe system 
containing a metal diaphragm designed to blow out when gas 
pressure exceeds a certain figure. 

Scale. The coating of oxide on (molten) iron and steel. 

Scaling Powder. Flux used for dissolving oxides formed 
in cast iron welding. 

Screen. A fine mesh wire cloth part to prevent foreign 
matter entering the regulator or torch. See Strainer. 

Scrubbing. An apparatus for removing ammonia, dust 
and other free impurities from acetylene gas. More elaborate 
than a washer. See Washer. 

Seam. A joint welded or unwclded. Applied generally 
to thin metal. 

Seat. The surface against which 'a valve disc is held 
when closed. 

Shell. The circular part of a cylinder. 

Side Seam. Applied to welding, meaning a horizontal 
seam in the side of an upright part. 

Slag. Oxidized metal and other impurities formed in 
welding 'and liable to be trapped in the molten state. Also 
applied to the oxidized metal and scale blown out when cut- 
ting iron and steel. 

Sludge. The accumulation of slaked carbide in the 
bottom of an acetylene generator. 

Sludge Valve. The discharge valve for removing resi- 
duum from an acetylene generator. 

Sodium Carbonate. (NaXOa) Carbonate of soda or 

13 



soda ash. 

Sodium Chloride. (NaCl) Common salt. 

Sodium Hydroxide. (NaOH) Caustic soda. Used in the 
electrolyte of oxygen and hydrogen generators. 

Sodium Silicate. (Na2Si409) Water glass. 

Sodium Sulphate. (NaoSO^) Glauber's salts. 

Sodium Tetraborate. (NaoB^O^) Borax. Crystalline borax 
contains ten parts water, its formula being Na2B4O-.+10H2O. 
Calcining or burning borax drives off the water of crystalliza- 
tion. 

Solder. A fusible alloy used for uniting metals. The soft 
solders melt at a comparatively low temperature and are 
alloys of lead and tin. The hard solders melt at higher 
temperatures and are usually alloys of zinc and copper. 

Soldering. The process of uniting metals by fusing an 
alloy of low melting temperature and heating the parts to be 
joined to the amalgamating temperature. 

Spectacles. Colored glasses with steel or aluminum 
frames and generally without side shields for protecting the 
eyes. 

Spelter. Hard solder, usually a one-to-one alloy of copper 
and zinc. 

Spoon. A wire flattened at the end for smoothing the 
surface of an aluminum joint welded without flux. 

Stirrup. The yoke connecting the diaphragm of a pres- 
sure regulator and the valve disc. 

Straightedge. Generally a steel bar with one edge planed 
straight and beveled. Used for lining up. 

Strainer. A part made of fine mesh wire cloth through 
which the gas passes and which stops the passage of dirt and 
foreign matter. 

Stuffing Box. The provision made for preventing gas 
leaking around the needle valve stems and high pressure valve 
stem of the cutting torch, etc. 

Sulphuric Acid. (H0SO4) Vitriol or oil of vitriol. 

Sweating. Soldering broad metal surfaces by coating the 
surface with solder, clamping the parts together and applying 
heat. 

14 



Tacking. Uniting metal parts with spots or buttons of 
fused metal. 

Tank. A pressure container for transporting acetylene, 
oxygen, hydrogen or other gas. See Cylinder or Bottle. 

Tinning. The process of coating metals with tin. Also 
applied to the preparation of tool steel for welding with 
machinery steel by coating the tool steel with adding material 
before welding. 

Tip. The copper or brass nozzle of the welding or cut- 
ting torch. 

Torch. A gas burner or blowpipe for welding or cutting. 

Torch Bushing. The nut for holding the tip in the torch 
head. 

Torch Head. The part of a ^welding or cutting torch 
carrying the tip. 

Torch Tube. The pipe connecting the torch head and 
handle. 

Ultimate Strength. The maximum load sustained* by a 
test bar before rupture. 

Union. A pipe coupling in parts held together with a 
nut. Used where pipes may require disconnection. 

Valve. The means for shutting off the flow of gas or 
liquid. 

Vee. The angle or groove between two beveled edges 
when prepared for welding. 

Vee Block. A block cut out in the shape of a vee or 
angle, and used for supporting shafts in line when welding. 

Vent Valve. Water sealed trap for discharging the 
excess water in an acetylene generator. Also a safety device 
to indicate the presence of an obstruction in the vent pipe. 

Vertical. Applied to welding, meaning a seam in an up- 
right or vertical position. 

Washer. An apparatus for removing ammonia and dust 
from acetylene gas. See Scrubber. 

Water Seal. A safety device to prevent backfires being 
propagated through a pipe line to the generator. 

Welding Rod. The metal used to supply the filler re- 
quired in a welded joint. Also called Adding Material and 

15 



Filler Rod. 

Welding Sticks. Adding material or welding rod of cast 
iron, cast aluminum and other cast metals. 

Welding Table. Metal table for supporting work for 
welding. 

Welding Wire. Wire adding material of the smaller 
gauges. 

Z-Bar. Structural shape having cross section similar to 
the letter Z. 

Zinc Chloride. (ZnCl,) Chloride of zinc or tinner's acid. 



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